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FRANKLIN  INSTITUTE  LIBRARY 

PHILADELPHIA,  PA. 


Class 


XZ.4L...  Book  J&SSLL  Accession  ...ZXX.XX 




Given  by 


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DEVELOPMENT 

OF 

Gelatine  - Dry  - Plates 


a practical  flDanual  for  tbe  amateur. 


R;ev.„W.  H.  lilJ.R  BANK,  . 

j j J J J J J > ' ) - ^ J 

j J J J J J J J ) ) J J 

Author  of  “ 'Pkpto^radJric  Priutjng  bTethoa  y,  ” ‘ The 
Photographic  Negative,"  Etc. 


BRUNSWICK,  MAINE  : 

W.  IT . BURBANK!, 
i 8 90. 


THE  GETTY  CENTER 
LIBRARY 


PREFACE. 


Of  making  books  photographic  there  is  seemingly  no  end, 
and  he  who  is  rash  enough  to  add  still  another  to  the  long 
list  may  well  be  asked  his  reasons  for  so  doing. 

In  the  present  case  it  is  hoped  that  a satisfactory  answer 
will  be  found  in  the  fact  that  there  is  at  present  no  exhaus- 
tive treatment  of  the  important  question  of  development 
readily  accessible  to  American  amateurs. 

The  foundation  of  a good  print  is  a good  negative,  and 
this  is  largely  a matter  of  skillful  development,  the  leading 
principles  of  which,  as  they  have  been  taught  me  in  my  own 
practice,  I have  endeavored  to  explain  in  plain  language  in 
the  following  pages. 

So  far  as  possible  I have  aimed  to  give  a reason  for  the 
formulas  and  methods  recommended,  and  I have  entered 
somewhat  at  length  into  the  theory  of  development,  in 
order  that  the  amateur  may  be  in  a position  to  compound 
his  developer  intelligently  and  with  reference  to  his  special 
needs. 

I have  not  sought  to  multiply  formulas  in  the  body  of  the 
book  ; I have  merely  taken  a typical  formula  under  each 
class  and  endeavored  to  make  its  method  of  action  and  its 
possible  modifications  so  plain  that  he  who  runs  may  read. 

To  the  great  army  of  amateur  photographers,  many  of 
whom  are  known  to  me  personally,  all  of  whom  I would  be 
glad  to  know,  this  attempt  to  make  smooth  the  somewhat 
difficult  path  of  development  is  most  heartily  dedicated  by 

The  Author. 


79  3-5¥- 


SPECIAL  LITERATURE  ON  DEVELOPMENT. 


Outside  of  current  periodical  literature,  which  is  full  of 
articles  on  the  subject,  the  following  special  works  have 
been  consulted  : 

“ Le  Developpement  de  L’lmage  Latente.”  By  A.  De 
La  Baume  Pluvinel  : Paris,  1889.  Gauthier-Villars  et  Fils. 

“Traite  Pratique  du  Developpement.'’  By  Albert 
Londe  : Paris,  1889.  Gauthier-Villars  et  Fils. 

“ Development.”  By  Lyonel  Clark  : London,  1890. 

Hazell,  Watson  & Viney. 

“The  Chemistry  of  Photography.”  By  Raphael  Mel- 
dola  : New  York  and  London,  1889.  Macmillan  & Co. 

To  the  first  and  last  of  these,  special  obligations  are  due 
foj  information  regarding  the  chemical  reactions  of 
development. 


CHAPTER  I. 


general  principles. 


HE  Latent  Image. — The  sensitive  surfaces  which  we 


have  to  consider  in  the  following  pages  are  formed  by 
coating  glass,  paper,  or  other  suitable  substance  with  a 
viscous  solution  of  gelatine,  holding  in  suspension  bromide 
of  silver  in  a more  or  less  finely  divided  state,  according  to 
the  degree  of  rapidity  of  the  emulsion.  When  such  sur- 
faces are  exposed  to  light,  either  in  the  camera  or  under  a 
negative,  the  sensitive  compound  undergoes  a change  of 
some  kind,  the  exact  nature  of  which  is  not  definitely 
known,  and  which  is  invisible  until  the  application  of  cer- 
tain reagents,  called  developers,  which  possess  the  property 
of  making  the  image  visible.  The  bromide  of  silver  is 
decomposed  wherever  it  has  been  affected  by  the  action  of 
light,  and  a dark  deposit  of  silver  is  formed  on  those  parts, 
in  exact  proportion  to  the  intensity  of  the  light-action. 

This  action  of  light  is  called  latent  or  actinic,  and  the 
invisible  image  is  a latent  image,  since  it  can  be  made  visible 
by  the  application  of  suitable  reagents. 

The  Nature  of  the  Latent  Image.  — Photographic 
scientists  are  by  no  means  in  agreement  respecting  the 
exact  nature  of  the  image  formed  by  the  action  of  light  on 
these  gelatino-bromide  surfaces.  Two  theories  have  been 
advanced  in  explanation  of  the  change  thus  produced  — the 
one  chemical,  and  the  other  physical.  According  to  the 
chemical  theory  the  image  produced  by  a short  exposure  t c 


5 


6 


Development  of  Dry  Plates. 


light  is  of  precisely  the  same  nature  as  that  produced  by  a 
prolonged  exposure,  that  is,  it  is  a partial  or  complete 
decomposition  of  the  bromide  of  silver,  which  is  reduced 
to  a sub-bromide.  If  the  action  of  light  has  been  suffi- 
ciently energetic  the  number  of  molecules  thus  reduced  is 
numerous  enough  to  produce  a visible  image.  In  the  case 
of  exposures  of  brief  duration  the  reduced  molecules  are 
too  few  in  number  to  produce  a visible  image,  and  a latent 
image  is  the  result. 

According  to  the  dynamic  or  physical  theory,  the  luminous 
rays  produce  a change  of  molecular  condition,  destroying 
the  equilibrium  previously  existing,  thus  producing  a new 
molecular  arrangement,  which  is  amenable  to  the  action  of 
the  developer.  The  reduced  or  changed  molecules  are  still 
molecules  of  bromide  of  silver,  only  in  a modified  condition. 

Owing  to  the  fact  that  the  direct  demonstration  of  the 
nature-of  the  change  is  at  present  quite  beyond  the  reach  of 
even  the  most  refined  chemical  methods,  it  is  impossible  to 
give  an  authoritative  statement  regarding  the  correctness  of 
either  of  the  above  theories,  but  inability  to  determine  the 
exact  nature  of  the  latent  image  does  not,  fortunately, 
seriously  affect  the  conditions  of  development.  We  know 
that  a change  of  some  kind  is  produced,  and  that  the  effects 
of  this  change  may  be  made  visible  and  permanent  by  the 
use  of  suitable  reagents.  How  best  to  do  this  is  the  sole 
object  of  the  following  pages. 

The  Possibility  and  Theory  of  Development. — Here, 
again,  positive  statement  is  not  permitted.  If  the  dynamic 
theory  be  accepted,  it  seems  probable  that  the  tendency  of 
the  action  of  light  upon  the  molecules  of  silver  bromide  is 
to  separate  them  and  thus  weaken  the  bonds  of  union 
between  them.  The  molecules  thus  separated  may.  be 


Development  of  Dry  Plates. 


7 


regarded  as  possessed  of  a certain  degree  of  potential 
energy,  by  which  they  are  enabled  to  exercise  a greater 
attraction  over  surrounding  bodies  than  is  exercised  by 
those  molecules  which  are  more  intimately  combined.  If  an 
exposed  plate  is  covered  with  a reagent  containing  silver  in 
a condition  of  easy  precipitation,  the  metal  is  attracted  by 
the  molecules  of  the  film,  which  have  been  acted  on  by 
light,  and  is  deposited  only  on  those  parts  of  the  film  which 
have  received  a light  impression,  and  in  exact  proportion  to 
the  intensity  of  that  impression.  The  image  is  thus  built 
up  by  accretion,  and  the  developers  which  act  in  this  way 
are  known  as  physical  developers.  This  is  the  usual 
method  of  development  for  collodion  plates. 

Instead,  however,  of  precipitating  the  stiver  on  the  sur- 
face of  the  exposed  film,  it  can  be  subjected  to  the  action 
of  a reagent  which  has  a reducing  power  over  the  modified 
molecules  of  silver  bromide.  In  this  case  the  molecules  of  the 
reagent  are  attracted  only  by  the  modified  molecules  of  the 
film,  and  the  decomposition  of  the  latter  takes  place  only  in 
those  parts  which  have  been  impressed  by  light.  In  this 
case  the  coloration  of  the  film  is  more  in  the  nature  of  a 
stain  than  a deposit,  as  in  the  former  case.  Developers 
which  act  in  this  way  are  called  chemical  developers,  and 
the  method  is  that  employed  in  the  development  of  gelatino- 
bromide  plates,  and  is,  therefore,  the  subject  of  this  book. 

Before  leaving  this  preliminary  treatment  of  the  subject, 
it  should  be  said  that  the  modified  bromide  of  silver  can  be 
completely  reduced  only  by  reagents  which  are  able  to  con- 
tinue the  separation  of  the  bromine  from  the  silver  begun 
by  the  action  of  light.  In  other  words,  the  developer  must 
be  a reducing  substance.  Such  substances  are  found  among 
those  bodies  which  have  a strong  oxidizing  power.  But  all 


8 


Development  of  Dry  Plates. 


easily  oxidizable  substances  are  not  equally  well  adapted 
to  the  development  of  the  latent  image.  Many  are  too 
powerful  to  be  used  for  this  purpose,  even  when  well 
restrained.  When  the  action  of  the  developing  agent  is 
too  powerful,  we  have  a general  reduction  of  silver  over  the 
entire  surface  of  the  plate,  producing  the  phenomenon 
familiarly  known  as  fog. 


CHAPTER  II. 


the  DEVELOPING  ROOM. 

A LTHOUGH  the  discussion  of  the  construction  and 
arrangement  of  the  developing  room  is  not  entirely 
germane  to  the  subject-matter  of  the  present  book,  a brief 
discussion  of  the  subject  does  not  seem  wholly  out  of  place 
in  view  of  the  important  part  which  the  developing  room 
plays  in  development.  I have  purposely  discarded  the  use 
of  the  time-honored  expression,  “ Dark  Room,”  as  being  a 
misnomer.  We  do  not  want  dark  rooms  when  we  develop 
our  plates.  We  want  rooms  abundantly  lighted  with  light 
of  a safe  quality.  I am  not  a believer  in  the  charms  of  an 
imperfectly  lighted  developing  room  in  which  the  chances 
of  success  are  appreciably  diminished  by  inability  to  deter- 
mine the  condition  of  things  in  the  developing  tray  at  a 
glance.  I prefer  to  have  an  abundance  of  light  and  .to 
provide  my  trays  with  covers  of  stout  cardboard  or  wood, 
removing  them  at  brief  intervals  to  examine  the  plate. 

It  is  obviously  impossible  to  give  any  hard  and  fast  de- 
tails for  the  construction  of  the  developing  room.  Indi- 
vidual needs  and  tastes  differ  so  much  that  what  would 
suit  one  would  be  of  no  value  for  another.  In  general  it 
may  be  said  that  the  room  should  be  of  fair  size.  Ten  by 
fourteen  feet  is  none  too  large  if  much  serious  work  is  to 
be  done  in  the  room.  If  possible,  it  is  well  to  have  another 
room  connected  with  the  developing  room  by  double  doors, 
for  such  photographic  operations  as  do  not  require  seclu- 

9 


io  Development  of  Dry  Plates. 

sion  from  daylight.  If  this  room  be  fitted  up  with  the 
usual  appliances  of  a laboratory,  including  a sink  and  run- 
ning water,  the  amateur  is  well  equipped  for  serious  experi- 
mental work,  which  should  form  a oart  of  the  education  of 
every  lover  of  the  science. 

The  developing  room  proper  should  be  provided  with 
double  doors  in  order  that  one  may  go  in  and  out  without 
fear  of  injury  to  the  sensitive  surface. 

The  Lighting. — I very  much  prefer  artificial  light  to 
daylight,  for  the  reason  that  it  is  more  constant  and  more 
easily  controlled.  Whenever  possible  the  source  of  light 
should  be  placed  outside  the  room,  to  avoid  heat  and  the 
products  of  combustion.  In  this  case  a large  opening  is  cut 
in  the  wall  immediately  over  the  sink.  At  least  three  sliding 
frames  should  be  fitted  to  the  opening,  one  glazed  with  plain 
ground  glass,  another  with  ruby  glass,  and  the  third  with 
yellow  glass.  If  orthochromatic  work  is  to  be  attempted, 
a fourth  frame,  covered  with  stout  brown  paper,  should 
be  added.  With  this  arrangement  the  operator  has  perfect 
control  over  the  quality  and  intensity  of  the  light,  both  of 
which  may  instantly  be  adapted  to  suit  the  work  in  hand. 

The  Sink.  — A lead-lined  wooden  sink  is  preferable  to 
one  of  iron  or  earthen  ware,  as  there  is  less  danger  of 
breaking  a plate  or  graduate  which  may  be  carelessly 
dropped.  It  will  be  found  advantageous  to  provide  two 
swinging  water-taps,  one  fitted  with  a fine  rose  and  the 
other  with  a plain  open  nozzle.  The  sink  should  be  of 
good  size  and  preferably  provided  with  a bottom  sloping 
from  the  sides  to  the  lowest  point  in  the  middle.  It  should 
be  fitted  with  a sliding  rack  on  which  to  place  the  develop- 
ing tray.  At  the  right  should  be  placed  the  hypo  tank  or 
tray  in  a position  to  be  free  from  all  chance  of  contaminat- 


Development  of  Dry  Plates. 


i 


in g other  chemicals.  Shelves  may  be  arranged  on  either 
side  of  the  window  over  the  sink  to  suit  individual  tastes. 
Beneath  the  sink  suitable  racks  for  trays  should  be 
arranged.  Fig.  i gives  a suggestion  for  the  construction 
of  a very  convenient  and  serviceable  sink. 


The  other  fittings  of  the  room,  such  as  shelves,  drawers, 
tables,  etc.,  are  best  left  to  the  fancy  of  each  worker. 
Efficient  and  light-tight  means  of  ventilation  should  be 
provided  and  the  question  of  heating  must  not  be  neg- 


12  Development  of  Dry  Plates. 

lected.  Fig.  2,  which  is  reproduced  from  M.  Londe’s  book 
on  Development,  shows  a very  effective  arrangement  of 
developmental  accessories.  On  the  right  of  the  sink  is 
seen  a very  simple  rocking  arrangement,  which  will  be 
found  a great  convenience  in  cases  of  prolonged  develop- 
ment. 

Of  course,  it  is  understood  that  successful  development 
is  not  conditioned  by  the  possession  of  such  elaborate  facili- 
ties as  are  described.  Good  work  is  possible  in  any 
darkened  room  with  a water  jug  and  a waste-water  pail  for 
accessories,  but  these  are  only  make-shifts,  and  have  no 
place  in  this  discussion. 

' A Portable  Developing  Room. — Figures  3 to  6 show  the 
details  of  construction  of  an  easily  constructed  developing 
room  which  combines  the  advantages  of  convenience  and 
portability.  It  can  be  taken  down  or  put  together  in  a 
short  time,  and  it  is  recommended  to  those  amateurs  to 
whom  the  first  of  May  brings  new  quarters,  or  who  do  not 
care  to  go  to  the  trouble  or  expense  of  building  a perma- 
nent abiding  place  for  the  Lares  and  Penates  of  develop- 
ment. The  cuts  are  taken  and  the  description  is  abridged 
from  the  pages  of  Der  Amateur  Photograph. 

Fig.  3 is  a perspective  view  of  the  room  showing  the 
method  of  construction.  A number  of  light  frames  of 
wood  covered  with  stout  pasteboard  or  sheathing  paper, 
forms  the  sides,  ends  and  top  of  the  structure,  which  may 
be  placed  in  a convenient  corner  of  any  available  room. 
One  of  the  frames  contains  a smaller  frame  mounted  on 
hinges  to  form  the  door.  As  to  size,  a room  6 feet  long, 
4/4  feet  wide  and  7 feet  high,  is  as  small  as  will  afford  the 
necessary  working  space.  The  width  is  governed  by  the 
width  of  the  work  table  and  the  space  to  be  left  between 


DEVELOPING  ROOM.  Fig. 


i4 


Development  of  Dry  Plates. 


Fig.  3. 


it  and  the  side  of  the  room.  In  joining  the  frames  the 
following  precautions  must  be  taken  to  insure  light-tight 

joints  : All  joints 

must  be  reinforced 
by  strips  of  thin 
wood  screwed  on 
both  sides.  Fig.  4 
shows  the  method 
of  protecting  the 
joints  on  the  two 
sides.  Fig.  5 shows 
the  method  of  pro- 
tecting the  corners, 
and  Fig.  6,  the  same 
principle  applied  to 
the  top  or  roof.  The 
door  must  fit  snugly  against  battens  fastened  to  the  inside 
of  the  frame.  Any  places  where  white  light  creeps  in  are 
easily  made  safe  by  pasting  black  paper  over  them.  In 
order  to  prevent  the  light  from  coming  around 
the  bottom  edge,  it  is  well  to  screw  half-inch 
cleats  to  the  floor  where  this  is  admissible, 
and  to  screw  the  bottoms  of  the  frames 
tightly  against  these.  f<g.  5. 

Fig.  7 shows  a very  con- 
venient work  table  for  such 
a room  as  this.  Its  con-  fig.  4. 

struction  is  so  plainly  shown  that  extended  description 
is  unnecessary.  The  dimensions  should  be  about 
three  feet  high,  three  feet  long  and  eighteen  inches 
wide.  That  portion  where  development  is  carried 
may  be  covered  with  sheet  lead  with  the  edges  turned 


on 


Development  of  Dry  Plates.  15 

up  about  half  an  inch  and  provided  with  a waste-pipe  lead- 
ing  to  a pail  underneath,  as  shown.  The  fixing  bath  is 
kept  in  a tray  on  the  shelf  under 
the  top  of  the  table.  This  shelf 
also  holds  the  washing  tray. 

Other  conveniences  may  be 
added  as  need  may  arise,  and 
the  room  will  be  found  a very 
decided  improvement  over  the 
out  - of  - the  - way,  inconvenient 
closets  which  serve  so  many 
for  developing  rooms. 

I have  intentionally  omitted 
all  mention  of  trays,  graduates, 
bottles,  and  the  other  impedi- 
menta of  the  well-stocked  de- 
veloping room.  Individual 
needs  and  circumstances  vary 
so  that  no  exhaustive  list  can  be  given.  All  these  things 
have  a way  of  accumulating  of  themselves  as  one’s  photo- 
graphic horizon  broadens,  and  their  acquisition  may  be  left 
to  the  purse  and  necessities  of  the  worker,  aided  by  the 
few  hints  which  I have  aimed  to  give  in  this  chapter. 


CHAPTER  III. 


tHe  principles  of  development  — tH  e tentative 

METHOD. 

OEFORE  entering  upon  the  more  practical  part  of  the 
subject,  it  will  be  well  to  give  what  I conceive  to  be  the 
underlying  principles  which  govern  all  good  development, 
and  since  in  doing  so  I shall  run  counter  to  the  advice  of  some 
good  authorities,  I desire  to  state  that  I believe  the  princi- 
ples which  I shall  advance  to  be  susceptible  of  proof  by 
actual  experience  in  the  developing  room.  They  are  given 
as  the  result  of  careful  study  of  the  conditions  which  seem 
to  me  to  govern  all  successful  development  of  the  latent 
image. 

My  experience  has  taught  me  that  something  more  is 
required  for  the  proper  development  of  the  latent  image 
than  the  possession  of  a good  formula  and  the  ability  to 
compound  it;  that  there  are  laws  of  development  which 
must  be  known  and  followed  before  the  operator  can  hope 
to  approach  development  intelligently.  These  laws  con- 
stitute what  we  may  term  the  philosophy  of  development. 
As  the  end  of  development  is  the  production  of  a negative 
which  will  yield  a print  of  a desired  quality,  the  first  step 
is  the  knowledge  and  appreciation  of  the  qualities  which 
the  various  printing  processes,  now  commonly  employed, 
demand  in  a negative.  There  is  no  question  here  of  sharp- 
ness of  outline  or  artistic  quality.  These  are  taken  for 
granted. 

Detail  and  intensity  must  be  placed  first  among  the  neces- 

16 


Development  of  Dry  Plates. 


T7 


sary  qualities  of  a good  negative.  There  must  be  no  large 
patches  of  blank  shadow,  and  the  density  must  be  propor- 
tioned to  the  printing  process  likely  to  be  used  in  making 
the  final  print. 

By  far  the  larger  portion  of  the  subjects  which  are  sought 
to  be  reproduced  by  means  of  photography  are  those  in 
which  there  is  an  infinite  gradation  of  tone  from  high  light 
to  intense  shadow.  Theoretically,  the  perfect  negative  is 
obtainable  only  under  the  condition  of  giving  to  each  por- 
tion of  the  subject  an  exposure  proportionate  to  the  rapidity 
of  its  action  on  the  sensitive  film.  But  this  is  evidently  an 
impossibility.  What  the  photographer  actually  does  in 
practice  is  to  give  an  equal  exposure  to  objects  unequally 
lighted,  thus  introducing  special  difficulties  in  the  later 
operation  of  development. 

Those  parts  of  the  subject  which  are  most  strongly  illu- 
minated act  with  greater  energy  on  the  sensitive  film  than 
those  less  strongly  lighted,  and  do  so,  probably,  in  direct 
proportion  to  the  degree  of  the  illumination.  Hence,  when 
the  developer  is  applied,  the  high  lights,  as  they  are  called, 
that  is,  those  portions  of  the  view  which  were  most  strongly 
illuminated,  appear  first,  and  are  followed  by  the  less 
intensely  lighted  portions,  and  these,  in  turn,  by  the  darker 
parts,  thus  giving  the  tone  gradation  which  is  so  marked  a 
characteristic  of  a good  negative. 

If  a proper  exposure  be  had  the  details  are  obtained  by 
continuing  the  development  until  these  are  well  out  in  the 
deepest  shadows.  Save  in  exceptional  cases,  no  part  of  the 
negative  should  be  devoid  of  a certain  amount  of  detail. 
From  this  we  may  deduce  the  first  general  rule  or  principle 
governing  development  : 

The  development  must  be  continued  until  all  the  detail  is  visible 


i8 


Development  of  Dry  Plates. 


in  the  clear  or  white  portions  of  the  negative , which  correspond 
to  the  shadows  of  the  subject. 

We  may  best  study  the  question  of  intensity  by  distin- 
guishing between  local  and  general  intensity.  The  former 
being  the  direct  result  of  the  unequal  lighting  of  the  sub- 
ject, it  reproduces  the  difference  of  tone  gradation.  It  is 
determined  by  the  intensity  of  the  rays  of  light  reflected 
from  the  different  parts  of  the  view,  and  it  is  generally 
independent  of  the  operator,  who,  however,  has  it  in  his 
power  to  modify  slightly  the  final  result. 

General  intensity  is  the  degree  of  density  which  must  be 
given  a negative  in  order  to  obtain  good  positives  from  it. 
There  must  be  a certain  degree  of  obstruction  to  the  free 
passage  of  light  through  different  portions  of  the  negative. 

It  is  quite  possible  for  a negative  to  have  detail  and  local 
intensity  without  being  a good  printer,  for  the  reason  that 
it  lacks  general  or  printing  density.  This  maybe  too  weak, 
in  which  case  the  print  will  be  monotonous  and  tame,  or 
it  may  be  too  strong,  giving  only  harsh  prints.  The  remedy 
in  the  first  case  is  intensification,  in  the  second  reduction, 
neither  of  which,  if  properly  conducted,  affects  the  local 
or  artistic  intensity,  for  if  it  did,  successful  intensification 
and  reduction  would  be  impossible. 

In  addition  to  the  rendering  of  detail,  then,  the  operator 
must  seek  to  give  his  negatives  the  degree  of  printing  den- 
sity best  suited  to  his  favorite  printing  process,  since  the 
different  printing  methods  require  negatives  of  varying 
density  — the  carbon  process  requiring  thin  and  harmonious 
negatives,  the  albumen  process  those  of  medium  density, 
and  the  platinum  process  those  of  greater  strength. 

Nothing  is  more  detrimental  to  successful  development 
than  the  belief  that  detail  and  density  can  be  secured  simul- 


Development  of  Dry  Plates. 


19 


taneously.  This  is  the  weakness  of  all  one-solution  devel- 
opers, that  they  are  based  on  the  false  assumption  that  detail 
and  density  go  hand  in  hand.  Only  in  the  case  of  negatives 
of  feeble  contrasts  and  proper  exposure  do  the  rendering 
of  detail  and  the  acquirement  of  printing  density  hold  an 
equal  place.  But  how  often  are  these  conditions  realized  ? 
Not  once  in  a hundred  exposures.  When  the  negatives 
present  strong  contrasts,  and  the  time  of  exposure  has  been 
more  or  less  wrong,  as  it  usually  is,  the  application  of  the 
developer  reveals  the  difficulty  of  obtaining  detail  and 
printing  density  at  one  and  the  same  time.  The  high  lights, 
which  are  the  first  to  appear,  continue  steadily  to  gain  in 
intensity,  and  long  before  the  details  in  the  shadows  are 
well  out,  the  density  of  the  high  lights  has  passed  the 
proper  degree.  Such  a negative  will  give  harsh  prints  in 
which  the  contrasts  are  exaggerated.  The  proper  method 
of  development  in  such  cases  is  to  hold  back  the  density 
until  the  details  are  well  out,  by  developing  for  detail 
first. 

In  the  opposite  case,  where  we  have  to  deal  with  exposures 
on  subjects  feebly  lighted  and  devoid  of  contrasts,  the  devel- 
opment must  be  for  density  first,  if  we  would  avoid  foggy 
and  weak  negatives.  This  gives  us  our  second  rule  or  prin- 
ciple of  development. 

If  these  principles  are  well  founded,  it  follows  that  a 
knowledge  of  the  best  methods  of  obtaining  both  density 
and  detail  is  essential  to  anything  like  true  development. 
These  methods  will  be  discussed  later  on.  As  a step  in 
this  direction,  I propose  now  to  discuss  briefly  the  condi- 
tions outside  of  the  developing  room,  which  have  much  to 
do  in  determining  both  detail  and  density. 

First  on  the  list  I place  the  influence  of  the  plate  itself. 


20 


Development  of  Dry  Plates. 


It  is  far  from  being  a matter  of  indifference  whether  we 
use  slow  or  rapid  plates.  No  manufacturer  of  sensitive 
plates  will  care  to  dispute  the  assertion  that  the  quality  and 
speed  of  the  plate  affect,  even  if  they  do  not  determine, 
the  finished  result. 

With  the  slower  grade  of  plates  printing  density  is  a mat- 
ter of  comparative  ease.  It  is  in  the  rendering  of  detail 
that  the  difficulty  begins.  With  rapid  plates  the  conditions 
are  reversed.  Detail  is  easily  rendered,  but  printing  den- 
sity does  not  always  accompany  this  rendering. 

Slow  plates  have  a tendency  to  increase  contrasts  unless 
the  time  of  exposure  is  purposely  prolonged  to  avoid  this 
difficulty.  Rapid  plates  tend  to  diminish  contrast  and  so 
to  produce  more  evenly  lighted  prints. 

For  the  beginner  there  is  nothing  better  than  plates  of 
medium  density,  since  they  have  not  the  same  tendency  to 
fogging  which  is  noticeable  in  rapid  plates,  always  remem- 
bering that  with  slow  plates  the  time  of  exposure  should  be 
lengthened  to  avoid  excessive  contrast,  while  with  rapid 
plates  the  time  of  exposure  should  be  made  as  short  as 
possible,  to  avoid  fog. 

Another  important  element  in  the  character  of  the  nega- 
tive and  consequently  of  the  print,  is  the  nature  of  the 
objects  to  be  reproduced.  Careful  study  of  the  view  to  be 
photographed  is  essential  to  success. 

M.  Londe’s  division  of  the  different  photographic  sub- 
jects is  so  true  and  helpful  that  I make  no  apology  for 
reproducing  it.  The  division  is  threefold  : 

First — Subjects  which  have  a perfect  harmony  of  tone 
gradation. 

Secondly  — Subjects  which  present  strong  contrasts  and 
oppositions. 


Development  of  Dry  Plates. 


21 


Thirdly — Subjects  which  have  not  enough  of  contrast 
and  opposition,  and  are,  consequently,  weak. 

Now,  it  is  very  evident  that  the  same  method  of  exposure 
and  development  cannot  be  adopted  in  all  these  cases,  that 
some  modifications  are  necessary  in  order  to  bring  out  the 
very  best  of  which  the  view  is  capable. 

It  is  a fact  established  by  observation  that  if  light  is 
allowed  to  act  upon  a sensitive  surface  the  effects  of  the 
light-action  increase  up  to  a certain  point,  and  that  beyond 
this  point  the  intensity  gradually  diminishes,  the  light 
seeming  to  destroy  the  effects  of  its  own  work. 

The  law  of  reduction  is  this  : The  intensity  of  reduc- 

tion is  directly  proportional  to  the  length  of  time  during 
which  the  addition  of  light  has  been  continued,  up  to  a 
certain  point,  which  for  any  given  plate  may  be  called  its 
fogging  point.  Beyond  this  point  the  effect  is  inversely  as 
the  action  of  light. 

In  practice,  then,  we  obtain  an  increasing  degree  of  in- 
tensity by  lengthening  the  time  of  exposure,  so  long  as  we 
keep  within  the  limit  where  the  inverse  action  begins. 

It  is  easy  to  see  the  importance  of  this  principle,  since 
the  knowledge  of  it  practically  applied  enables  us  to 
modify  at  will  the  results  of  an  exposure. 

With  subjects  of  the  first  class  the  time  of  exposure 
should  be  as  nearly  correct  as  it  is  possible  to  make  it. 
Subjects  of  the  second  class  should  be  somewhat  over 
exposed,  both  in  order  to  secure  the  detail  in  the  dimly 
lighted  portions  and  to  reduce  the  density  of  the  high  lights. 
Subjects  of  the  third  class  require  a brief  exposure  in  order 
to  increase  the  contrasts. 

The  reader  who  has  followed  me  intelligently  thus  far  is 
prepared  to  profit  by  the  succeeding  remarks  on  the  general 


22 


Development  of  Dry  Plates. 


principles  of  development,  which  are  here  given  only  after 
a thorough  test  of  their  value  in  the  developing  and  print- 
ing rooms. 

As  the  pyro  developer  is  more  flexible  than  any  other  in 
common  use  I have  taken  it  as  the  standard  of  judgment, 
but  the  principles  are  equally  applicable  to  all  forms  of 
developers. 

In  the  development  of  an  exposed  plate  either  of  two 
methods,  the  automatic  and  the  tentative,  may  be  adopted. 
I use  the  expression  automatic  development  with  reference 
to  that  method  in  which  the  plate  is  left  in  a ready  mixed 
solution  without  any  modifications  being  made  to  suit  the 
seeming  exigencies  of  the  case.  All  one  solution  develop- 
ers, as  well  as  those  in  which  a given  formula  is  blindly 
followed,  come  under  this  head.  I have  a well-founded 
distrust  and  lack  of  confidence  in  the  method  of  automatic 
development,  which  is  rapidly  becoming  popular  with 
amateurs  of  a certain  class,  whose  one  aim  seems  to  be  to 
reduce  photography  to  a mere  mechanical  routine. 

The  tentative  method  of  development,  which  I believe  to 
be  the  only  rational  and  philosophical  method,  is  based 
upon  the  wise  and  intelligent  adaptation  of  means  to  ends. 

Starting  with  a thorough  knowledge  of  the  leading 
features  of  the  view  on  the  plate,  and  a perfect  under- 
standing of  the  effects  to  be  produced,  the  various  ingredi- 
ents of  the  developer  are  to  be  so  proportioned  as  to  lead 
up  to  the  desired  result.  From  time  to  time  as  need  arises 
various  modifications  are  made.  “Festina  lente  ” is  the 
motto  of  this  method.  A wise  caution  is  exercised  at  the 
outset,  constant  vigilance  is  maintained  till  the  end  of  the 
development,  and  a wise  intelligence  recognizes  and  meets 
all  the  exigences  of  the  case  as  they  present  themselves. 


Development  of  Dry  Plates. 


23 


I would  lay  it  down  as  an  axiom  seldom  to  be  deviated 
from  that  all  development  should  begin  slowly  with  a 
developer  relatively  weak  in  both  accelerator  and  reducer. 
In  this  way  the  image  will  not  surprise  one  by  a sudden 
appearance  and  an  equally  sudden  disappearance  in  a veil  of 
fog.  So  far  from  beginning  with  a bath  of  maximum  or  even 
normal  energy  I would  advise  a bath  of  minimum  strength 
save  in  those  special  cases,  to  be  mentioned  later,  where  a 
different  method  is  absolutely  necessary.  . In  this  way  the 
operator  remains  an  easy  master  of  the  development. 

Several  methods  of  reducing  the  strength  of  the  de- 
veloper are  open  to  the  operator.  He  may  either  diminish 
the  quantity  of  the  components  of  the  solution,  or  dilute  it 
with  water,  or  finally  add  a trace  of  bromide.  It  is  by  no 
means  a matter  of  indifference  which  of  these  methods  is 
adopted,  since  each  modification  produces  a different  effect. 

The  diminution  of  the  quantity  of  the  accelerator  and 
reducer  is  valuable  chiefly  because  it  allows  a wider  range 
of  subsequent  modification  to  suit  special  needs. 

The  addition  of  bromide  retards  the  development  and 
tends  to  increase  contrast.  Hence,  its  use  is  indicated  for 
negatives  of  evenly  lighted  subjects  where  all  possible  con- 
trast is  sought.  When  the  developer  is  diluted  with  water 
the  development  proceeds  slowly,  because  the  constituents 
of  the  solution  are  not  present  in  sufficient  quantities  to 
produce  a rapid  reduction.  The  tendency  of  a diluted 
bath  is  to  produce  softness,  and  it  should  be  employed  in 
cases  of  known  over-exposure  when  softness  is  desired. 

If  the  development  was  begun  with  a bath  weak  in  alkali 
and  reducer,  and  it  is  desired  to  bring  out  the  details 
before  giving  printing  density,  as  is  usually  the  case,  suc- 
cessive small  additions  of  the  alkali  are  made  until  the 


24 


Development  of  Dry  Plates. 


detail  in  the  shadows  is  well  out,  then  a final  addition  of 
pyro  confers  printing  density. 

As  an  example,  let  us  take  the  case  of  a subject  of  strong 
contrasts  which  was  intentionally  over-exposed  to  diminish 
the  contrasts.  The  proper  method  of  development  would 
be  to  begin  with  a small  percentage  of  pyro  and  carbonate, 
in  the  developer,  adding  the  carbonate  gradually  in  small 
quantities  until  the  details  are  well  out  in  the  shadows.  If 
the  development  were  stopped  at  this  point  we  should  have 
a negative  full  of  detail  and  of  good  local  density,  but 
lacking  in  general  or  printing  density.  This  is  gained  by 
adding  pyro  until  the  general  density  is  judged  to  be 
sufficient. 

If  the  whole  amount  of  pyro  ultimately  employed  had 
been  present  in  the  solution  from  the  start,  the  result  would 
have  been  a negative  in  which  density  had  been  reached 
before  the  details  were  all  out,  the  contrasts  would  be  too 
strong,  and  it  would  present  the  appearance  of -an  under- 
exposed plate. 

If  the  view  belongs  to  the  third  class,  that  is,  if  it  lacks 
contrast  and  opposition,  density  must  be  given  before  the 
details  are  entirely  brought  out,  by  the  addition  of  the 
carbonate  in  smaller  quantities  and  the  use  of  pyro  to 
confer  density. 

This  is  the  only  rational  method  of  development,  and  the 
fact  that  it  requires  intelligence  on  the  part  of  the  operator 
should  be  an  argument  in  its  favor  with  those  who  regard 
photography  as  something  more  than  a press-the-button,  one- 
solution  sort  of  business.  It  is  the  only  method  which  gives 
the  operator  an  easy  mastery  of  his  negative  and  enables 
him  to  produce  effects  of  various  kinds.  It  is,  I have  reason 
to  believe,  the  method  of  the  masters  in  photography. 


CHAPTER  IV. 


THE  automatic  method— tHe  Use  of  bromide 
over-exposUre. 

A UTOMATISM  in  photography  has  followed  the  ad- 
vent  of  the  dry  plate  and  the  discovery  of  methods  of 
combining  the  elements  of  a developer  in  one  solution  of 
good  keeping  qualities.  To  make  automatic  photography 
more  easy,  ingenious  cameras  have  been  devised  which  do 
away  with  focussing,  time  exposures  and  most  of  the  rou- 
tine of  the  older  school.  I am  as  ready  as  any  one  to  recog- 
nize the  value  of  the  new  photography  for  many  purposes, 
but  I must  protest  against  its  being  taken  for  all  there  is  to 
photography. 

Similarly,  I do  not  deny  that  one  solution  developers 
have  a certain  value,  but  I maintain  that  they  cannot  pro- 
duce the  highest  results. 

The  reign  of  automatic  developers  may  be  said  to  have 
begun  with  the  general  introduction  of  hydrochinon  as  a 
developing  agent.  It  was  found  to  be  much  easier  to  make  a 
stable  solution  with  hydrochinon  than  with  pyro,  and  as  it 
unquestionably  simplified  the  process  of  development,  much 
enthusiasm  was  manifested  by  its  advocates.  In  another 
chapter  I have  tried  to  state  the  hydrochinon  case  as 
fairly  as  possible.  Here  I wish  to  say  a few  words  about 
automatic  development,  meaning  by  this  expression  the 
development  of  a negative  without  any  of  the  modifica- 
tions mentioned  in  Chapter  III.  Theoretically  the  time  of 
exposure  is  not  an  element  of  importance  with  this  method. 

25 


26 


Development  of  Dry  Plates. 


All  the  operator  is  required  to  do  is  to  place  the  exposed 
plate  in  this  magical  one-solution  developer,  take  an  occa- 
sional look  at  it  and  remove  it  when  it  is  done,  just  as  the 
cook  removes  the  Thanksgiving  turkey  from  the  oven. 

For  every  subject  there  is  a time  of  exposure  which  we 
may  call  normal,  the  time  that  is  required  for  all  the  de- 
tails to  impress  themselves  on  the  plate.  Corresponding  to 
this  normal  exposure  there  is,  we  may  suppose,  a normal 
developer,  that  is  a developer  which  in  a certain  time  will 
produce  a negative  rich  in  detail  and  of  the  proper  general 
density.  Now,  if  it  were  possible  to  determine  the  exact 
normal  exposure  for  every  subject,  automatic  development 
would  become  a possibility.  In  other  words,  it  would  be 
possible  to  develop  every  negative  in  a developer  of  the 
same  constitution  and  in  the  same  time.  The  exposure 
having  been  normal,  the  development  would  be  normal  as 
well. 

But  the  moment  the  normal  time  of  exposure  is  exceeded 
or  not  reached  that  moment  the  normal  developer  beomes 
practically  useless.  For  every  length  of  exposure  there  is 
a developer  which  will  give  the  best  results.  What  this 
developer  is,  can  only  be  determined  by  adopting  the  ten- 
tative method  of  development.  The  negative  may  belong 
to  any  one  of  the  three  classes  mentioned  in  the  last  chap- 
ter, requiring  special  treatment  which  cannot  be  applied  in 
the  automatic  method. 

I have  no  hesitation  in  saying  that  it  is  almost  an  impos- 
sibility to  produce  two  negatives  of  precisely  the  same 
quality  in  any  one-solution  developer.  Although  no  visible 
change  may  take  place  in  the  solution,  either  through  use 
or  age  a change  is  produced  nevertheless,  which  affects  the 
result.  ' 


Development  of  Dry  Plates. 


27 


If  any  one  doubts  this  assertion,  he  has  only  to  make, 
say,  three  exposures  on*the  same  subject  under  similar 
conditions  of  light,  exposure  and  plate.  Let  one  of  these 
exposures  be  developed  for  a given  time  in  any  one-solu- 
tion developer.  Let  the  other  exposures  be  put  away  in  a 
safe  place,  and  at  the  end  of  two  varying  periods  of  time 
let  them  be  developed  in  the  same  solution  for  the  same 
length  of  time.  Unless  my  experience  is  greatly  at  £ault, 
a marked  difference  will  be  noticeable  in  the  three  nega- 
tives — a difference  which  can  come  from  no  other  cause  than 
a chemical  change  in  the  developer,  the  possibility  of  which 
is  sufficient  to  condemn  the  one-solution  developer  for  the 
highest  grade  of  work.  One  other  reason  is  sufficient  to 
condemn  the  use  of  single  solution  developers.  Most  of 
these  solutions  are  purchased  from  dealers  and  the  buyer 
has  no  knowledge  of  their  composition.  He  cannot  there- 
fore modify  them  intelligently  and  he  thus  places  himself 
at  the  mercy  of  his  developer. 

The  use  of  Bromide. — As  bromide  is  naturally  a retarder 
of  development,  at  first  sight  it  might  seem  that  the  proper 
corrective  of  over-exposure  would  be  the  addition  of  brom- 
ide in  a quantity  proportionate  to  the  degree  of  the  over- 
exposure. A more  philosophical  way  of  stating  the  prin- 
ciple governing  the  use  of  bromide,  would  be  to  say  that 
the  amount  of  bromide  must  be  proportional  to  the  inten- 
sity of  the  action  produced  by  light. 

This  is  the  general  law,  but,  like  most  other  laws,  it  has 
its  exceptions.  In  negatives  of  harsh  contrasts  where  the 
time  of  exposure  has  been  purposely  exaggerated,  the  use 
of  bromide  is  interdicted,  since  it  would  produce  the  very 
effect  we  are  seeking  to  avoid.  We  then  use  a minimum 
of  bromide  and  a diluted  solution. 


28 


Development  of  Dry  Plates , 


The  use  of  bromide  is  recommended  for  negatives  of 
poorly  lighted  subjects  in  order  t&  heighten  the  contrasts. 

There  seems  to  be  very  little  choice  among  the  two  brom- 
ides commonly  used.  The  bromide  of  potassium  is  a more 
stable  compound  than  the  corresponding  ammonium  salt, 
and  its  use  is  therefore  advised.  Bromide  of  sodium  is  also 
a good  restrainer.  The  bromides  of  zinc  and  copper  seem 
to  work  best  with  the  eikonogen  developer. 

Intentional  Over-Exposure. — There  are  occasions  when 
a judicious  lengthening  of  the  exposure  will  improve  the 
quality  of  the  negative,  but  the  method  is  hardly  to  be 
recommended  to  the  beginner,  and  in  any  event  it  is  to  be 
used  with  extreme  caution,  and  preferably  with  slow  plates. 
In  spite  of  frequent  statements  to  the  contrary,  I maintain, 
and  am  prepared  to  prove  the  statement,  that  with  intelli- 
gently-conducted development,  the  time  of  exposure  within 
reasonable  limits,  is  not  the  all-important  matter  it  is  said 
to  be.  The  statement  which  I make  is,  that  the  proper 
time  of  exposure  may  be  increased  without  producing  in- 
jurious results. 

Every  one  is  aware  that  there  exists  for  each  class  of 
subjects,  with  a plate  of  a given  rapidity,  a time  of  expos- 
ure which  we  may  call  the  time  of  normal  exposure,  since 
it  is  the  time  the  plate  must  be  exposed  in  order  to  render 
all  the  detail  combined  with  good  general  density. 

Now,  if  this  normal  time  is  diminished,  some  of  the  de- 
tails will  be  lacking.  If  it  is  exceeded,  the  details  will  be 
all  impressed,  but  there  will  be  danger  of  fog  through 
over-exposure.  It  is  plain  that  what  light  has  not  ef- 
fected, no  developer,  however  powerful,  can  make  visible. 
Hence,  an  under-exposed  plate  cannot  be  developed  into  a 
satisfactory  negative. 


Development  of  Dry  Plates . 


29 


It  has  already  been  shown  that  an  over-exposed  plate 
can  be  satisfactorily  developed,  either  by  the  use  of  brom- 
ide or  by  a diluted  or  weak  developer.  Hence,  it  would 
seem  to  follow  that  the  safest  plan  would  be  to  over-ex- 
pose and  to  modify  the  developer-  accordingly,  and  this  is 
what  I commonly  do  in  my  own  practice,  and  what  I recom- 
mend to  others;  only  one  must  know  his  subject  and  his 
plate. 

By  adopting  the  tenative  method  of  development,  I find 
no  difficulty  in  making  good  negatives  on  plates  which 
have  received  at  least  double  the  normal  exposure,  and  as 
this  increase  in  exposure  makes  me  sure  of  the  details,  I 
have  long  used  it,  except  in  special  cases  where  for  reasons 
already  given  a short  exposure  is  called  for. 


CHAPTER  V. 


THE  components  OF  THE'  developer 
ANd  tHeir  adjustment. 

'T'HE  method  of  alkaline  development  is  undoubtedly  the 
A one  which  admits  of  the  widest  range  of  modification  to 
suit  the  ever-varying  conditions  which  present  themselves 
in  the  developing  room.  In  all  alkaline  developers  there 
are  three  elements  : i,  pyrogallol,  or  its  equivalent  ; 2,  an 
alkali  ; 3,  a bromide. 

The  solution  of  the  problem  of  development  will  be  ma- 
terially aided  by  a consideration  of  the  function  which  each 
of  these  elements  is  called  upon  to  fulfil  and  their  relation 
to  each  other. 

Pyrogallol,  or  its  equivalent,  is  a powerful  absorbent  of 
oxygen  and  a reducer  of  the  modified  bromide  of  silver. 
Hence,  it  is  the  reducing  or  developing  agent.  The  inten- 
sity or  density  of  the  deposit  is  largely  conditioned  by  the 
quantity  of  the  reducing  agent  present  in  the  developer. 
Hence,  additional  density  is  conferred  by  an  increased  amount 
of  pyrogallol  or  its  equivalent.  By  judiciously  proportion- 
ing the  amount  of  the  oxidizing  agent,  almost  any  degree 
of  density  may  be  given  to  a negative.  To  some  extent 
the  same  effect  is  produced  by  increasing  the  affinity  of  the 
reducer  for  oxygen  by  increasing  the  quantity  of  alkali,  or 
by  decreasing  it  by  the  addition  of  a soluble  bromide.  It 
is  not,  however,  a matter  of  indifference  which  of  these 
methods  of  controlling  density  is  adopted.  An  increase  in 
the  quantity  of  alkali  increases  the  danger  of  fog  by  pro- 

30 


Development  of  Dry  Plates. 


3i 


ducirig  an  undue  rapidity  in  the  reduction  process.  An 
excess  of  bromide  so  diminishes  the  action  of  the  reducer 
as  to  make  the  bringing  out  of  fine  detail  difficult,  if  not 
impossible.  It  will  be  seen,  therefore,  that  the  developer 
must  be  compounded  with  a modicum  of  brains  in  order  to 
obtain  the  best  results. 

There  must  be  a proper  balance  between  the  ingredients  of 
the  developer,  or  partial  or  total  failure  will  be  the  only  result. 

The  problem  which  has  to  be  solved  with  every  plate  is 
to  bring  out  all  the  detail  possible  and  at  the  same  time  to 
obtain  good  general  or  printing  density,  and  this  without 
the  slightest  trace  of  veil  or  fog. 

The  alkali  aids  in  the  attainment  of  detail  by  increasing 
the  affinity  of  the  reducer  for  oxygen,  and  the  bromide  has  a 
strong  tendency  to  diminish  the  chance  of  fog  by  slowing  the 
reducing  action.  It  is  probable  that  the  restraining  power 
of  the  bromide  is  due  to  its  tendency  to  form  a double  salt 
with  bromide  of  silver,  this  double  salt  being  more  stable 
than  the  silver  bromide  and  therefore  less  easily  reducible. 

If  the  reducing  agent  were  always  used  in  a dry  state, 
that  is,  if  for  purposes  of  convenience  it  were  not  desirable 
to  make  up  a stock  solution  to  be  drawn  from  as  need  arose, 
no  other  elements  would  be  needed  than  those  just  men- 
tioned. Since,  however,  a stock  solution  is  often  a neces- 
sity, it  has  been  found  necessary  to  add  various  substances 
to  the  solution  of  pyrogallol  to  prevent  its  rapid  deteriora- 
tion by  oxidization.  Of  these  substances  the  sulphite  and 
meta-bisulphite  of  soda,  meta-bisulphite  of  ammonium,  for- 
mic, citric  and  other  acids  have  been  used  with  good  re- 
sults. The  best  of  these  is  probably  the  meta-bisulphite  of 
soda  or  ammonium,  either  of  which  will  preserve  a solution 
of  pyrogallol  for  a moderate  length  of  time. 


32 


Development  of  Dry  Plates. 


The  objection  to  the  use  of  sulphite  of  soda  is  its  tend- 
ency to  pass  over  into  sulphate  of  soda,  which  is  a powerful 
restrainer. 

My  own  custom  is  not  to  employ  a stock  solution,  but  to 
add  the  reducing  agent  in  a dry  state  to  the  developer, 
thus  dispensing  entirely  with  the  use  of  a preservative, 
which  seems  to  me  to  be  a needless  if  not  an  injurious 
complication.  The  simpler  we  keep  our  formulas  the 
greater  our  chances  of  success. 

Modifications. — With  alkaline  developers  containing 
pyrogallol  a very  wide  range  of  modification  to  suit  vary- 
ing needs  is  possible.  The  normal  proportions  of  the  com- 
ponents of  the  developer  may  be  taken  to  be  nearly  as  fol- 
lows: Pyrogallol,  0.5  parts  ; alkali,  2 to  6 pa'rts  ; sulphite,  3 
parts;  bromide,  0.5  parts;  water,  100  parts  ; or  for  each 
ounce  of  developer,  3 grains  of  pyrogallol ; alkali,  10  to  30 
grains ; sulphite,  14  grains  ; bromide,  3 grains. 

These  proportions,  however,  may  be  changed  to  suit 
special  circumstances.  It  is  time  now  to  speak  of  some  of 
the  more  important  of  these  modifications,  and  I shall  treat 
the  subject  with  reference  to  the  pyrogallol  developer,  since 
this  is  the  one  most  commonly  employed. 

As  I have  already  said,  I am  an  advocate  of  a moderately 
slow  development,  and  strongly  deprecate  the  use  of  a bath 
at  its  maximum  of  energy  to  begin  development  with.  It 
is  much  safer  in  every  way,  especially  in  all  cases  where 
one  is  in  doubt  whether  the  exposure  has  been  correct  or 
not,  to  begin  with  a solution  at  its  minimum  energy. 

Several  methods  of  reducing  the  energy  of  the  developer 
are  possible.  The  quantity  of  the  elements  of  the  solution 
may  be  diminished,  the  bath  itself  may  be  diluted  with 
water,  or  bromide  may  be  added.  Which  of  these  methods 


Development  of  Dry  Plates. 


33 


is  to  be  employed  in  each  case  of  known  over-exposure 
will  depend  upon  the  character  of  the  subject  and  the 
effect  which  it  is  desired  to  produce. 

The  addition  of  bromide  retards  the  action,  but  at  the 
same  time  tends  to  increase  contrast  and  give  density. 
The  dilution  of  the  bath  equally  retards  the  action  but  has  no 
tendency  to  increase  contrast  or  produce  excessive  density. 

The  use  of  bromide  is  indicated  for  the  development  of 
subjects  uniformly  lighted  and  presenting  no  strong  con- 
trasts, in  order  to  heighten  the  contrasts.  On  the  other  hand, 
if  the  view  was  strongly  lighted  and  presented  great  opposi- 
tion, which  it  is  desired  to  diminish  as  far  as  possible,  the 
normal  bath  should  be  diluted  with  water.  If  the  subject 
was  well  illuminated  and  the  contrasts  well  balanced  and 
harmonious,  the  development  should  be  begun  in  a bath 
weak  in  pyro  and  alkali,  developing  first  for  detail  and  lastly 
for  density.  This  result  is  obtained  by  adding  successive 
small  doses  of  the  alkali  at  intervals  until  the  details  in 
the  shadows  are  well  out  and  then  obtaining  the  density  by 
a final  addition  of  the  necessary  amount  of  pyrogallol. 

With  subjects  of  feeble  contrast  the  method  should  be 
reversed.  Here  the  aim  should  be  to  retard  as  much  as 
possible  the  appearance  of  the  details  by  a wise  caution  in 
the  addition  of  the  alkali,  and  to  gain  the  greatest  possible 
density  by  adding  sufficient  pyrogallol  to  accentuate  as 
much  as  possible  the  feeble  values  of  the  subject. 

Density. — One  of  the  greatest  difficulties  connected  with 
development  for  the  beginner  is  to  know  the  exact  moment 
when  the  process  of  development  should  be  stopped,  that  is, 
when  sufficient  printing  density  has  been  obtained.  Of  the 
many  negatives  which  I have  examined,  including  many  of 
my  own,  there  have  been  few  which  were  removed  from  the 


34 


Development  of  Dry  Plates. 


developer  at  just  the  right  moment.  Either  they  were  taken 
from  the  bath  too  soon  and  lack  printing  density,  or  they 
were  allowed  to  remain  too  long  in  the  developer,  and  are 
over-dense  to  give  the  best  results  in  the  printing  frame. 

It  is  not  an  easy  matter,  even  for  the  most  expert,  to 
determine  in  the  light  of  the  developing  room  the  exact 
moment  when  the  proper  degree  of  density  has  been 
reached.  Indeed,  I am  not  certain  that  it  is  not  largely  a 
matter  of  intuition,  gained  only  by  long  practice  and  not 
to  be  learned  from  written  words.  Still  some  hints  may  be 
given  which  may  help  a stumbling  brother  along  the  diffi- 
cult road  of  development. 

In  general  terms,  it  is  best  to  allow  the  developer  to  act 
until  those  parts  of  the  plate  which  have  been  feebly  im- 
pressed, that  is,  those  which  remain  white  longest,  begin 
to  darken.  With  certain  brands  of  plates,  which  lose 
strength  in  the  fixing  bath,  it  is  safe  to  prolong  the 
development  until  the  edges  of  the  plate  which  were  pro- 
tected from  the  action  of  light  by  the  ledges  of  the  slides 
show  a slight  veiling.  If  a plate  be  examined  at  this  stage 
by  reflected  light,  it  will  show  a uniform  dark  tint.  Ex- 
amined by  transmitted  light  the  image  will  appear  over- 
vigorous  and  the  finer  details  somewhat  clogged  up. 
With  some  plates  it  is  even  necessary  to  allow  the 
developer  to  act  until  the  image  seems  to  have  disap- 
peared entirely.  A properly  developed  plate  should  show 
the  image  feebly  on  the  back.  A generally  safe  rule  is  to 
develop  until  the  blacks  and  the  strongest  half-tones  are 
plainly  visible  at  the  back  of  the  plate,  but  much  depends 
on  the  character  of  the  plate  and  the  method  by  which  the 
prints  are  to  be  made.  A properly  exposed  and  normally 
developed  plate  should  be  finished  within  five  minutes. 


CHAPTER  VI. 


THE  FERROUS-OXALATE  developer. 

/^HEMICAL  Reactions.  — When  a sensitive  surface 
which  has  been  exposed  to  light  is  placed  in  a solu- 
tion of  ferrous-oxalate,  the  following  reactions  take  place  : 

The  ferrous-oxalate  decomposes  the  water,  changes  into 
ferric-oxalate  and  ferric-oxide,  while  the  hydrogen  of  the 
water  is  set  at  liberty. 

6(C204Fe)  + 3H20  = 2 [(C204)3Fe2]  + Fe20*6H. 
6(Fe0,C203)  4-  3HO  = 2(Fe203,3C203)  + Fe2Q3-f  3H. 

The  hydrogen,  thus  set  at  liberty,  acts  upon  the  modified 
bromide  which  it  reduces  : 

AgBr  + H = Ag+HBr. 

The  hydrobromic  acid,  formed  by  this  reaction,  acts  upon 
the  ferric-oxide  of  the  previous  reaction  and  produces  fer- 
ric-bromide and  water  : 

6HBr  + Fe2Os  = Fe2Br6  + 3H20. 

3HBr  + Fe203  - Fe2Br3  4-  3HO. 

Adding  these  three  equalities,  we  have  as  the  final  chem- 
ical expression  of  the  reaction  : 

6(C204Fe)  + 6 AgBr  - 2 [(C204)3Fe2]  4-  6Ag  + Fe2Br3, 
6(Fe0,C203)  + 3 AgBr  = 2(Fe203,3C203)  4-  3Ag-|-  Fe2Br2. 

The  modified  bromide  of  silver  is  decomposed  by  the 
ferrous-oxalate,  the  reduced  silver  forms  the  lights  of  the 

35 


36  Develop7?ient  of  Dry  Plates . 

image,  and  there  remain  in  the  bath  ferric-oxalate  and  fer- 
ric-bromide. 

Preparation  of  the  Developer. — The  developer  con- 
sists of  a solution  of  ferrous-oxalate.  This  salt  is  formed 
when  a ferrous  salt  is  added  to  a solution  containing 
an  oxalate  or  oxalic  acid.  If  a solution  of  neutral 
potassic  oxalate  is  added  to  a solution  of  ferrous  sulphate 
the  liquid  becomes  red,  grows  muddy,  and  deposits  yellow 
crystals  of  ferrous-oxalate,  which  is  nearly  insoluble  in 
water,  but  readily  soluble  in  warm  solutions  of  the  neutral 
oxalates  of  potassium  or  sodium.  It  is  in  combination  with 
solutions  of  these  salts  that  the  ferrous-oxalate  is  employed 
as  a developing  reagent.  Its  best  solvent  is  a saturated 
solution  of  neutral  potassic  oxalate.  100  parts  of  this 
solution  dissolve  12  parts  of  ferrous  oxalate.  A saturated 
solution  of  potassic  oxalate  contains  1 part  of  the  salt  to  3 
of  water.  In  order  to  prepare  100  parts  of  the  developer, 
33  parts  of  neutral  potassic  oxalate  are  dissolved  in  100 
parts  of  water,  and  12  parts  of  ferrous  oxalate  are  added 
to  the  warm  solution. 

The  more  usual  method  of  preparing  the  developer  is  to 
form  the  ferrous  salt  and  dissolve  it  at  the  same  time. 
This  is  easily  done  by  adding  one  part  of  a saturated  solu- 
tion of  sulphate  of  iron  to  three  parts  of  a saturated  solu- 
tion of  neutral  potassic  oxalate.  In  this  case  the  potassic 
salt  plays  a double  part  : One  part  forms  the  ferrous  oxa- 

late, while  the  other  part  acts  as  the  solvent. 

As  the  proportions  of  oxalate  and  sulphate  are  deter- 
mined by  the  solubility  of  the  salts,  they  cannot  be  in- 
creased in  order  to  strengthen  the  developing  action.  If 
an  excess  of  the  sulphate  is  added,  a precipitate  of  ferrous 
oxalate  is  thrown  down  and  the  bath  loses  its  reducing 


Development  of  Dry  Plates.  37 

power.  It  is  important  also  that  the  potassic  oxalate  be 
neutral.  An  acid  sample  will  not  give  clear  images. 

If  the  water  employed  to  dissolve  the  potassic  salt  con- 
tains sulphate  of  chalk,  a slight  trace  of  oxalate  of  chalk  is 
formed  and  the  solution  is  not  clear.  As  soon  as  the  solu- 
tion cools,  however,  the  chalk  will  deposit  and  the  clear 
liquid  may  then  be  decanted  off  for  use  in  compounding 
the  developer.  To  avoid  the  precipitate,  distilled  rain  or 
melted  ice  water  should  be  used. 

The-  mixed  developer  does  not  keep  well  without  the  ad- 
edition  of  some  substance  capable  of  reconverting  the 
ferric  sulphate  to  the  corresponding  ferrous  salt.  Tartaric 
acid  has  this  property,  and  old  solutions  may  be  restored  to 
activity  by  adding  a trace  of  the  acid  and  standing  the  bot- 
tle in  the  sun.  The  tartaric  acid  is  oxidized  at  the  expense 
of  the  ferric  sulphate,  which  returns  to  the  ferrous  state. 

We  are  now  prepared  to  give  a definite  formula  for  the 
preparation  of  the  developer,  and  the  following  has  given 
me  uniformly  good  results  : 

A.  Neutral  oxalate  of  potash, 30  parts. 

Water, 100  parts. 

B.  Sulphate  of  iron, 30  parts. 

Tartaric  acid, o.  5 parts. 

Water, 100  parts. 

This  solution  will  keep  indefinitely  if  placed  in  the  sun- 
light when  not  in  use  : 

C.  Bromide  of  potassium, 1 part. 

Water, 10  parts. 

This  is  the  restrainer,  and  is  to  be  used  only  in  case  of 
over-exposure,  or  with  very  rapid  plates  to  diminish  the 
danger  of  veiling. 


3« 


Development  of  Dry  Plates. 


Development  of  Plates  Normally  Exposed. — When 
the  exposure  has  been  correctly  timed,  the  percentage  of 
one  to  three  should  be  diminished.  My  own  practice  is 
to  add  one  part  of  solution  B to  ten  parts  of  A.  If  the 
high  lights  begin  to  appear  in  one  or  two  minutes,  the 
exposure  has  been  about  correct,  and  the  plate  is  trans- 
ferred to  a tray  containing  one  part  of  A to  four  of  B,  and 
the  development  is  completed  in  this  stronger  developer. 
If  for  any  reason  exceptional  density  is  desired,  a few 
drops  of  C should  be  added.  In  any  case  the  action  of  the 
developer  is  to  be  continued  until  the  image  seems  to  have- 
disappeared  and  is  quite  plainly  visible  at  the  back  of  the 
plate. 

Development  of  Under-exposed  Plates.  — If  a three 
or  four  minutes’  treatment  with  the  one  to  ten  solution 
produces  no  visible  effects,  the  plate  should  be  treated 
for  under-exposure.  For  this  purpose  it  is  transferred 
to  a tray  containing  the  strong  one  to  three  solution.  If 
this  does  not  produce  the  desired  effect  within  a few  mo- 
ments, the  plate  was  probably  too  slightly  acted  upon  by 
light  to  make  successful  development  possible,  there  being 
too  slight  an  amount  of  modified  bromide  present  in  the 
film  for  the  developer  to  act  upon.  Something  may 
possibly  be  effected  by  the  addition  of  a drop  or  two  of  a 
i to  2.000  solution  of  hyposulphite  of  soda,  itself  a power- 
ful reducer.  This  addition  is  always  attended  with  danger, 
owing  to  its  strong  tendency  to  produce  fog. 

Development  of  Over-exposed  Plates.  — If  the  image 
comes  up  quickly  and  evenly  in  the  one  to  ten  solution, 
the  plate  must  be  treated  for  over-exposure  by  removing 
it  at  once  to  a dish  containing  one  part  of  solution 
C to  ten  parts  of  water.  A few  drops  of  C are  then 


Development  of  Dry  Plates. 


39 


added  to  the  developer  and  the  plate  returned  to  it.  Un- 
less the  time  of  exposure  was  greatly  exaggerated,  the 
image  will  develop  gradually  and  strongly  in  this  modified 
developer.  It  is  always  best,  however,  to  have  a quantity 
of  old  developer  at  hand  for  use  with  over-exposed  plates. 
Many  skillful  operators  recommend  the  addition  of  one 
part  of  old  developer  to  three  of  freshly  mixed  for  the 
development  of  landscape  views,  and  the  method  has  its 
advantages. 


CHAPTER  VII. 


THE  pYROGALLoL  developer. 


HEMICAL  Reactions. — Pyrogallol,  or  pyrogallic  acid, 


(C6H603,C1 2H606)  is  a white  powder  extracted  from 
gall  nuts  or  by  treating  gallic  acid.  It  dissolves  in  2.5  its 
weight  of  water,  and  is  readily  soluble  in  alcohol  and  ether. 

When  exposed  to  atmospheric  influences  its  solutions 
rapidly  oxidize,  absorbing  oxygen  from  the  air  with  the 
formation  of  certain  obscure  brown  products  and  such  acids 
as  oxalic,  acetic  and  carbonic,  according  to  the  following 
formula  : 

C6H603  -f-70  = C2H304-|-C2H403  -f-2COs, 

C12H606  14O  = C4H208-}-  C4H404  + 4CO2. 

The  addition  of  an  alkali  to  a solution  of  pyrogallol 
greatly  increases  its  avidity  for  oxygen,  and  in  consequence 
its  reducing  power  on  the  salts  of  silver.  A plain  solution 
of  pyrogallol  Will  develop  an  exposed  plate  but  only  with 
great  slowness.  Its  action  is  hastened  by  the  addition  of 
an  alkali  which  quickens  the  development  by  acting  upon 
the  acids  arising  from  the  oxidation  of  the  pyrogallol,  and 
by  combining  with  the  hydrobromic  acid  produced  by  the 
decomposition  of  water.  A bromide  of  the  alkali  is  thus 
formed  in  the  developer. 

The  following  formula  expresses  the  complex  reaction  : 


C6H603+2AgBr+2AzH3+H20  = (C6H603+0)+2Ag-|-2AzH4Br, 
C 1 2 H « O « q- AgBr+ AzH  3 +HO = (C 4 2 H 6 O 6 +0)-l- Ag+ AzH  4 Br. 

40 


Development  of  Dry  Plates. 


4i 


This  formula  expresses  the  reactions  which  take  place 
when  an  exposed  plate  is  developed  in  a solution  of  pyro- 
gallol with  ammonia  as  the  alkali. 

Preparation  of  the  Bath. — The  pyrogallol  developer 
must  consist  of  the  acid  and  an  alkali.  This  alkali  may  be 
either  ammonia,  potash,  or  soda  either  as  carbonates  or 
sulphites.  In  England,  ammonia  has  been  the  alkali  most 
commonly  used.  In  America,  soda  or  potash,  or  both  com- 
bined, are  usually  preferred. 

The  action  of  these  alkalis  is  not  the  same.  Ammonia 
is  probably  stronger  in  detail  giving  power,  and  produces 
better  modeled  negatives,  but  its  use  is  attended  with 
greater  danger  of  fog.  Carbonate  of  potash  seems  to  have 
more  power  over  the  rendering  of  detail  than  the  corre- 
sponding salt  of  soda,  while  the  latter  is  a better  density 
giver.  With  either  of  these  salts  there  is  less  danger  of 
fog  than  with  ammonia,  but  they  have  a more  decided 
tendency  to  frill  the  plate.  On  the  whole,  however,  my 
personal  preference  is  for  a developer  containing  both  the 
carbonates  of  potash  and  soda,  with  sufficient  sulphite  of 
soda  added  to  insure  a clean  development. 

A normal  developer  with  ammonia  is  compounded  as  fol- 
lows : 

Water, 100  parts. 

Pyrogallol, 0.3  parts. 

Ammonia, o.  5 parts. 

Bromide  of  potassium, 0.5  parts. 

The  proportion  of  ammonia  may  safely  be  increased  to 
three  parts,  but  it  should  not  exceed  this.  The  amount  of 
pyro  may  be  doubled  or  trebled  if  necessary  to  obtain 
density. 


42 


Development  of  Dry  Plates. 


The  following  may  be  taken  as  a normal  potassic  car- 


bonate developer  : 

Water, ioo  parts. 

Pyrogallol, 0.5  parts. 

Carbonate  of  potassium, o.  5 parts. 


The  amount  of  carbonate  may  safely  be  increased  to  five 
parts,  if  necessary,  and  the  amount  of  pyrogallol  to  two  or 
three  parts. 

A normal  soda  developer  is  given  in  the  following  formula: 


Water, 100  parts. 

Carbonate  of  sodium, 1 to  5 parts. 

Pyrogallol, 0.4  parts. 


A good  combined  soda  and  potash  formula  is  as  follows: 


Water, 100  parts. 

Pyrogallol, 0.5  parts. 

Carbonate  of  soda,  . 2 parts. 

Carbonate  of  potash, 1 part. 


Preservatives. — The  baths  prepared  as  above  discolor 
rapidly  during  development,  and  the  plate  becomes  more 
or  less  tinged  with  yellow.  In  the  case  of  thin  negatives 
this  yellowishness  is  an  advantage,  since  it  has  a tendency  to 
increase  contrast,  but  most  operators  prefer  to  avoid  it  so 
far  as  possible,  or  to  remove  it  after  fixing.  The  latter  is 
attained  by  placing  the  negative  in  a bath  of  dilute 
sulphuric  acid  containing  a little  alum  to  counteract  the 
frilling  effect  of  the  acid. 

The  discoloring  of  the  bath  is  due  to  oxidation,  which  is, 
in  turn,  caused  by  the  reduction  of  the  silver  salt  and  by 
the  absorption  of  oxygen  from  the  air.  This  process  of 
oxidation  may  be  greatly  retarded  by  the  addition  of  some 


Development  of  Dry  Plates . 


43 


substance  which  has  greater  affinity  for  oxygen  than  the 
pyrogallol.  Such  substances  are  sulphite  of  soda,  the 
meta-bisulphites  of  soda  and  ammonium  and  many  others 
of  similar  nature.  Either  of  these  three  salts  will  produce 
the  desired  result  by  absorbing  oxygen  from  the  air  and 
leaving  the  pyrogallol  free  to  deal  with  the  modified  silver 
salt.  Until  recently  sulphite  of  soda  has  been  almost  exclu- 
sively employed,  but  lately  the  meta-bisulphites  have  been 
used  with  better  results. 

The  proportion  of  preservative  may  vary  from  three 
parts  to  one  hundred  to  much  larger  quantities.  A typical 
formula  of  this  class  is: 


Water, ioo  parts. 

Pyrogallol, 0.5  parts. 

Carbonate  of  potash, 1 part. 

Sulphite  of  soda, 3 parts. 


If  a little  sulphuric  acid  is  added  to  th-e  solution  it  will 
unite  with  the  sulphite  of  soda  to  form  sulphurous  acid, 
which  is  a powerful  deoxidizer. 

Sulphite  of  soda,  either  in  crystals  or  in  solution,  easily 
passes  over  into  sulphate  of  soda,  which  is  not  a preserva- 
tive, but  which  has  strong  restraining  qualities.  In  order 
to  test  the  purity  of  a given  sample  of  sulphite,  it  is  treated 
with  hydrochloric  acid.  The  sulphurous  acid  is  set  free 
and  chloride  of  sodium  is  formed.  When  the  sulphite  is 
entirely  decomposed,  chloride  of  barium  is  added  to  the 
solution.  If  any  sulphate  is  present,  a large  quantity  of  a 
white  precipitate  is  formed. 

Sulphite  of  Soda  as  a Developer. — Apart  from  its 
preservative  action,  sulphite  of  soda  has  a certain  power  of 
development.  It  can  develop  the  latent  image  without  the 


44 


Development  of  Dry  Plates. 


addition  of  any  other  alkali.  The  development  is  slow, 
but  the  image  is  very  pure  and  bright.  For  very  much 
over-exposed  plates  sulphite  of  soda  has  a value  which  is 
not  at  present  properly  recognized. 

For  other  formulas  the  reader  is  referred  to  the  tables  at 
the  end  of  the  book. 

The  developing  solution  is  conveniently  compounded  by 
adding  to  three  ounces  of  water  6 grains  of  dry  pyrogallol, 
12  to  30  grains  of  carbonate  of  potash  and  10  to  20  grains 
of  sulphite  of  soda,  according  to  the  plate  and  the 
exposure. 

Development  of  a Normally  Exposed  Plate.-— My 
own  method  of  development  is  to  make  up  1 to  10  solu- 
tion of  the  carbonate  and  sulphite. 

For  a 5x8  plate  three  ounces  of  water  are  placed  in  the 
tray,  six  to  ten  grains  of  dry  pyrogallol  and  half  an  ounce 
of  the  sulphite  solution  are  added.  When  the  pyrogallol  is 
dissolved,  the  plate  is  immersed  in  the  tray,  and  at  the  end 
of  half  a minute  the  developer  is  poured  off  into  a graduate 
and  one  dram  of  the  solution  of  the  carbonate  is  added. 
This  is  allowed  time  to  act.  If  the  high  lights  do  not 
show  themselves  within  one  or  two  minutes,  another  addi- 
tion of  carbonate  is  made,  the  tray  being  constantly  rocked 
to  insure  equal  action.  The  image  will  soon  show  itself 
under  this  treatment  and  it  will  probably  gain  in  detail  and 
density  until  the  process  is  complete.  If,  however,  the 
details  in  shadows  are  slow  in  appearing,  more  carbonate 
is  added.  If  good  general  density  is  not  obtained  more 
pyrogallol  is  added,  and  in  some  cases  a few  drops  of  a 
one  to  ten  potassic  bromide  solution.  In  any  case  the 
development  is  continued  until  the  image  is  plainly  visible 
at  the  back  of  the  plate. 


Development  of  Dry  Plates. 


45 


Development  of  Under-Exposed  Plates. — If  the  plate 
after  a prolonged  immersion  in  the  above  bath  shows  a 
general  want  of  vigor  and  detail,  it  has  been  under-ex- 
posed, and  the  bath  must  be  modified  in  order  to  meet  the 
conditions  of  the  case.  In  order  to  understand  the  nature 
of  these  modifications,  a thorough  knowledge  of  the  action 
of  each  of  the  components  of  the  bath  is  necessary.  This 
knowledge  I now  propose  to  impart  to  the  best  of  my  ability. 

The  alkali  has  a double  function  ; one  portion  is  used  in 
neutralizing  the  acids  which  are  formed  in  the  bath  and 
thus  accelerates  the  action.  The  amount  of  alkali  taken 
up  by  this  action  varies  according  to  the  quantity  of 
pyrogallol  present.  The  remaining  portion  of  the  alkali 
remains  free  in  the  bath  and  acts  directly  upon  the  plate. 
The  tendency  of  the  alkalis  is  to  transform  the  bromide  of 
silver  into  the  modified  state.  Hence,  the  alkali  which  is 
free  to  act  upon  the  plate  modifies  that  portion  of  the 
bromide  which  has  been  feebly  impressed  by  light,  and 
tends  to  bring  it  into  the  same  molecular  state  as  the 
bromide  which  has  received  a more  energetic  light-impres- 
sion. Hence,  the  alkali  acts  as  an  accelerator  and  dimin- 
ishes contrast. 

If  a large  amount  of  pyrogallol  is  added  the  bath 
becomes  more  concentrated  and  the  development  more 
rapid.  But  -at  the  same  time  the  amount  of  free  alkali  is 
diminished  and  its  action  on  the  bromide  of  silver  is 
lessened.  Hence,  the  increased  addition  of  pyrogallol  to 
the  bath  is  equivalent  to  diminishing  the  amount  of  alkali, 
and  has  the  further  effect  of  increasing  contrast. 

From  this  somewhat  abstruse  reasoning,  which  seemed 
to  be  necessary  to  a complete  understanding  of  the  subject, 
we  may  easily  deduce  the  best  course  to  follow  in  the 


46 


Development  of  Dry  Plates . 


development  of  under-exposed  plates.  If  the  plate  has  a 
tendency  to  fog,  the  quantity  of  alkali  must  be  diminished, 
otherwise  the  plate  will  probably  veil  over  and  nothing  but 
a monotonous  image  be  developed.  Hence  the  proportion 
of  alkali  to  pyrogallol  must  be  diminished.  The  develop- 
ment will  proceed  slowly  but  the  image  will  acquire  the 
requisite  density,  which  it  would  not  have  done  had  the 
opposite  course  been  taken. 

. If  the  plate  is  a good  fog  resister,  as  is  the  case  with 
most  slow  plates,  and  the  contrasts  are  harsh,  the  alkali 
must  be  increased  and  the  pyrogallol  diminished.  The 
alkali  has  a tendency  to  veil  the  plate  and  so  to  produce 
soft  images.  When  the  details  are  well  out,  the  develop- 
ment is  completed  by  the  addition  of  pyrogallol  to  give 
sufficient  density. 

Contrast  may  also  be  diminished  by  allowing  the  devel- 
oper to  remain  at  rest  during  the  development.  This  is 
due  to  the  fact  that  the  developer  rapidly  loses  its  energy 
where  it  is  in  contact  with  the  heavy  shadows  which  have 
been  most  strongly  impressed,  and  retains  it  longest  where 
it  is  in  contact  with  the  half-tone,  since  here  it  does'  not  so 
soon  become  saturated.  But  this  method  can  be  adopted 
only  when  the  bath  has  been  considerably  diluted.  A 
strong  bath  would  in  this  case  produce  markings. 

Development  of  Over-Exposed  Plates. — When  a plate 
has  been  over-exposed  the  contrasts  are  diminished  and 
the  likelihood  of  fog  increased.  For  both  these  reasons 
it  is  necessary  to  begin  the  development  with  a small 
amount  of  alkali  and  an  excess  of  pyrogallol.  Bromide  of 
potassium  may  also  be  added,  and  should  be  so  added  to 
the  normal  developer  when  the  image  flashes  up  at  once 
on  the  application  of  the  bath. 


CH  APTE  R VIII. 


tHe  HYdrocHiNoN  developer. 

T TYDROCHINON  or  quinole  is  an  aniline  derivative 
**  prepared  by  oxidizing  aniline  sulphate  with  potassic 
bichromate.  Its  chemical  symbol  is  C6H602,  and  owing  to 
its  powerful  reducing  power  and  its  comparative  freedom 
from  fog  and  stain,  it  has  gained  many  friends  and  is  now 
quite  generally  employed.  Chief  among  the  many  advantages 
claimed  for  the  quinole  developer  are  : simplicity  and  ease 

of  working ; the  great  latitude  of  exposure  allowed  ; ab- 
sence .of  fog  and  stain  ; clear  glass  in  the  shadows  ; suita- 
1 bility  for  bromide  paper  work. 

On  the  other  hand  the  developer  has  a strong  tendency 
to  give  harsh  negatives,  full  of  excessive  contrast.  It  often 
produces  yellow  fog  or  stain,  and  it  is  extremely  slow  in 
action. 

On  the  whole,  after  careful  experiments  with  quinol,  I 
have  found  it  decidedly  inferior  to  pyrogallol  in  the  major- 
ity of  cases.  Still  it  has  some  excellent  qualities,  and  I 
would  recommend  the  amateur  to  master  its  method  of 
working  as  a help  to  the  solution  of  difficult  problems  in 
the  developing  room.  Many  a negative  which  shows  lack 
of  general  density  under  the  action  of  the  pyrogallol  devel- 
oper may  be  brought  up  to  the  printing  point  by  the  applica- 
tion of  an  old  quinol  solution. 

I have  been  most  successful  with  the  formulae  and 
method  of  preparation  recommended  by  the  Paris  Photo- 

47 


48 


Development  of  Dry  Plates. 


graphic  Club,  which  is  as  follows  : Boil  one  quart  of  distilled 
or  ice  water  and  divide  equally  into  two  quart  bottles  ; while 
still  warm,  add  to  one  of  the  bottles  250  grains  of  sulphite  of 
soda  in  crystals,  to  the  other  add  500  grains  of  sodic  carbon- 
ate in  crystals,  both  salts  having  been  previously  powdered. 
Shake  well  until  dissolved.  To  the  sulphite  solution  add  150 
grains  of  quinol  and  shake  until  dissolved,  then  add  8 to  ro 
drops  of  glacial  acetic  acid.  When  the  two  solutions  are  cold 
the  quinol  solution  is  poured  rapidly  into  the  carbonate,  and 
the  mixture  is  then  filtered.  The  mixed  solution  forms  a 
powerful  developer  which  keeps  well  and  works  satisfac- 
torily. For  time  exposures,  it  should  be  diluted  one-half 
with  water,  or  equal  parts  of  new  and  old  developer  may 
be  used  to  advantage. 

Another  good  formula  is  the  following: 

Quinol,  .........  15  grains. 

Citric  acid,  7 ‘ ‘ 

Sodium  sulphite, 60  “ 

Water  to  make 3^  ounces. 

The  caustic  alkalis  are  often  used  when  a more  speedy 
action  is  desired.  The  best  method  of  using  them  seems  to 
be  the  addition  of  about  5 <f0  of  a 40$  solution  of  caustic 
potash  just  before  development. 

Mr.  Henry  J.  Newton  recommends  the  following  for- 
mula: 


Water, 1 ounce. 

Caustic  soda, 4 grains. 

Sulphite  of  soda, 30  “ 

Hydrochinone, 3 “ 


This  forms  a good  developer  for  instantaneous  expo- 


Development  of  Dry  Plates. 


49 


sures  : for  time  exposures,  the  strength  should  be  reduced 
from  one-half  to  one-third  with  water. 

Good  results  can  be  obtained  on  nearly  all  brands  of  dry 
plates  with  any  of  the  above  formulae,  but  I have  found 
that  certain  makes  of  plates  do  not  take  kindly  to  quinol, 
quickly  veiling  over. 

As  a rule,  it  will  be  found  advisable  to  add  a trace  of 
bromide  of  potassium  to  the  bath,  and  to  follow  the  gen- 
eral method  of  development  recommended  for  pyrogallol. 
Development  will  be  begun  with  a weak  bath  and  its  energy 
will  be  gradually  increased,  if  necessary,  by  the  gradual 
addition  of  the  alkali  to  bring  out  detail. 

The  bath  should  be  used  at  its  maximum  strength  only 
in  cases  of  known  under  exposure.  The  best  results  are 
obtained  by  the  judicious  use  of  a new  and  an  old  bath. 
The  longer  the  exposure,  the  greater  the  proportion  of  the 
old  bath  ; short  exposures  require  a smaller  percentage  of 
old  bath.  Where  strong  contrasts  are  desired,  an  old  bath 
is  to  be  used.  For  soft,  harmonious  effects  the  quantity  of 
new  bath  should  be  increased. 

Although  the  same  solution  can  undoubtedly  be  used  to 
develop  a number  of  negatives  in  succession,  it  must  not  be 
forgotten  that  the  bath  loses  its  strength  with  use.  With 
each  plate  developed  the  composition  of  the  bath  changes 
and  it  works  more  slowly  and  with  greater  contrast.  If  a 
number  of  negatives  are  to  be  developed  in  the  same  solu- 
tion, it  is  best  to  begin  with  a weak  bath  and  to  develop 
the  negatives  in  the  order  of  their  times  of  exposure,  be- 
ginning with  that  which  received  the  shortest  exposure.  It 
will  also  be  found  necessary,  now  and  then,  to  strengthen 
the  bath  by  the  addition  of  more  alkali.  This  same  method 
is  also  recommended  for  other  forms  of  developer. 


5° 


Development  of  Dry  Plates. 


When  the  development  has  been  unduly  prolonged,  the 
negative  often  shows  a yellow  stain.  This  may  be  removed 
by  the  application  of  Farmer’s  ferricyanide  and  hypo 
reducer  which  will  be  found  under  the  formulae  for  reduc- 
ing agents. 

On  the  whole,  I cannot  recommend  the  quinol  developer 
as  in  any  way  superior  or  even  equal  to  pyrogallol.  It  has 
all  the  deficiencies  of  the  latter  and  is  devoid  of  many  of 
its  good  qualities.  I am  convinced  that  more  detail  can 
usually  be  obtained  and  better  printing  negatives  made 
with  pyrogallol  than  with  quinol. 

For  negatives  where  great  purity  in  the  lines  is  necessary, 
as  in  the  case  of  reproductions  and  slides,  quinol  undoubt- 
edly possesses  some  advantages,  but  for  landscapes  this 
same  excess  of  transparency  produces  harshness  in  the 
prints. 


CHAPTER  IX. 


THe  eiKoMogeN  aNd  pYrocatecHiN  developers. 

T7  IKONOGEN  is  an  aniline  derivative  of  great  reducing 
power  which  has  recently  come  into  general  use  as  a 
developing  agent,  owing  as  much  perhaps  to  judicious  and 
persistent  advertising  as  to  its  intrinsic  merits,  which,  though 
great,  are  not  overwhelmingly  superior  to  those  of  pyrogallol. 
About  the  same  claims  are  made  for  the  new  reagent  as  for 
quinol.  It  works  rapidly,  has  no  pronounced  tendency  to 
produce  fog  or  stain,  keeps  fairly  well  in  solution,  and  is 
strong  in  power  to  bring  out  detail.  Its  great  weakness  is 
a varying  degree  of  solubility  with  different  samples  and  a 
tendency  to  give  thin  negatives. 

I have  not  found  that  a solution  of  eikonogen  keeps 
appreciably  better  than  a properly  prepared  pyrogallol  solu- 
tion, but  as  I always  use  both  reagents  dry,  I do  not  con- 
sider this  an  important  point.  Eikonogen  certainly  does 
bring  out  detail  more  rapidly  than  other  developers,  but  in 
the  end  I have  not  usually  found  a greater  amount  of 
detail  in  a negative  developed  with  it  and  one  of  the  same 
subject,  similarly  exposed,  developed  with  pyrogallol. 
Some  operators  have  claimed  that  it  was  not  an  uncommon 
experience  with  them  to  develop  a negative  with  eikonogen 
and  fix  it  while  another  was  developing  in  a pyrogallol  bath, 
but  my  experience  does  not  bear  out  this  statement. 

But  this  is  not  to  say  that  eikonogen  is  not  a most  excel- 
lent developer.  I am  now  using  it  largely  in  preference  to 

51 


52 


Development  of  Dry  Plates. 


pyrogallol  on  account  of  its  general  freedom  from  liability 
to  fog  or  stain  the  negative.  It  gives  as  clear  negatives  as 
quinol  with  much  less  of  harshness  and  excessive  contrast, 
and  it  possesses  remarkable  staying  powers.  I have  devel- 
oped as  many  as  twenty  5x8  negatives  in  the  same  solution 
with  no  appreciable  lengthening  of  development  or  change 
in  the  quality  of  the  negatives. 

My  favorite  formula  and  method  of  working  are  as 
follows  : 

A.  Water, 1 ounce. 

Sulphite  of  Soda, 40  grains. 

Eikonogen, ; 20  “ 

Dissolve  in  the  order  given.  With  some  samples  of 
eikonogen  it  will  be  found  impossible  to  dissolve  the  above 
amount,  but  this  seems  to  make  no  appreciable  difference. 
The  water  should  be  distilled  and  hot. 


B.  Distilled  water, 1 ounce. 

Carbonate  of  potash, 50  grains. 

Sulphite  of  sodium, 50  “ 


In  both  solutions  the  crystallized  sulphate  is  used.  These 
are  strong  solutions  and  are  to  be  mixed  in  equal  parts  for 
short  exposures.  For  time  exposures  the  mixed  developer 
should  be  judiciously  diluted  with  water,  the  greater  the 
proportion  of  water  the  softer  the  negative. 

Solution  A will  retain  its  good  qualities  for  several  weeks 
if  pure  chemicals  and  distilled  water  are  used. 

My  own  practice  is  to  dissolve  the  proper  amounts  of 
sulphite  and  eikonogen  in  distilled  water  immediately  before 
using. 


Development  of  Dry  Plates . 


53 


If  the  image  flashes  up  immediately  on  the  application 
of  the  developer,  the  negative  is  quickly  transferred  to  a 
tray  containing  4 grains  of  bromide  of  potash,  1 cfram  of 
glycerine  and  10  ounces  of  water,  which  is  allowed  to  act 
for  two  or  three  minutes,  after  which  the  plate  is  returned 
to  the  developer. 

If  no  trace  of  an  image  appears  within  two  or  three 
minutes,  two  or  three  drops  of  a 10-grain  solution  of  caustic 
soda  may  be  added. 

If  the  developer  as  above  compounded  works  too 
rapidly  the  amount  of  water  in  solutions  A and  B should 
be  doubled. 

Another  equally  good  formula  is  that  recommended  for 
use  with  the  Cramer  plate,  but  which  I have  found  to  work 
well  with  most  other  makes. 


A.  Distilled  water, 10  ounces. 

Sulphite  of  soda  (crystals),  ....  240  grains. 

Eikonogen, 120  “ 

B.  Water,  10  ounces. 

Carbonate  of  potassium, 1 ounce. 

C.  Water, 10  ounces. 

Bromide  of  potassium,  ......  1 ounce. 

NORMAL  DEVELOPER. 

Solution  A, 3 ounces. 

“ B, I ounce. 

“ C, 6 to  12  drops. 


A mixture  of  old  and  new  developer  is  recommended  for 
general  work. 

Soft,  harmonious  negatives  are  produced  by  the  addition 
of  water. 

To  sum  up  the  case  in  favor  of  eikonogen,  it  may  be  said 
that  while  the  extravagant  claims  of  the  introducers  of  the 


54 


Development  of  Dry  Plates. 


new  reagent  have  not  been  confirmed  by  careful  experiment, 
it  is  a valuable  addition  to  the  list  of  photographic  chemi- 
cals. It  is  probable  also  that  further  experiments  may  give 
an  increased  ability  to  work  the  salt  to  better  advantage. 
As  a developer  for  instantaneous  exposures,  I regard  it  as 
greatly  superior  to  either  pyrogallol  or  hydrochinone, 
bringing  out  all  possible  detail  and  giving  good  general 
density  if  it  is  given  time  to  act.  The  negatives  are,  as  a* 
rule,  perfectly  free  from  fog  or  stain  and  of  a good  printing 
color. 

The  Pyrocatechin  Developer. — Pyrocatechin,  C6H4 
(OH2),  although  recommended  as  a developer  by  Dr.  Eder 
as  long  ago  as  1880,  has  never  come  into  general  use,  in 
spite  of  its  many  excellent  qualities,  on  account  of  its  high 
price. 

In  conjunction  with  carbonate  of  potash  it  is  a quick  act- 
ing and  powerful  developer,  giving  clear  negatives  of  a 
beautiful  brown  tone. 


The  solution  quickly  turns  a 

deep  brown  and  does  not 

keep  well.  The  following  formula  has  given  good  results 
in  my  hands  : 

A.  Water,  .... 

Sulphite  of  soda,  . 

. . . . 4 parts. 

Pyrocatechin,  . . 

B.  Water,  .... 

Carbonate  of  soda, 

. . . . I part. 

Normal  developer  : Equal  parts  of  A and  B.  Restiain, 

if  necessary,  with  bromide  of  potassium. 

If  the  cost  of  the  salt  can  be  reduced,  it  will  undoubtedly 
assume  a prominent  place  among  the  developers  of  the 
future. 


CHAPTER  X. 

development  of  instantaneous  exposures, 
films  aNd  Lantern  slides. 

T NSTANTANEOUS  EXPOSURES.— The  problem  to  be 
A solved  in  the  development  of  plates  which  have  been 
but  feebly  impressed  by  light  is  to  obtain  all  the  details  that 
can  be  forced  out  without  producing  an  undue  degree  of 
density.  At  the  outset  it  may  be  stated  that  no  developer 
will  bring  out  on  a plate  details  which  the  action  of  light 
has  not  first  impressed  upon  the  sensitive  surface.  The  de- 
tails must  be  present  potentially  or  they  can  not  be  made 
visible  by  the  action  of  the  developer. 

Authorities  are  divided  on  the  question  as  to  whether  a 
weak  or  a strong  developer  should  be  used  for  instantaneous 
work.  M.  Londe  recommends  a concentrated  solution, 
strong  in  reducer  and  accelerator,  with  a trace  of  bromide 
added  and  a smaller  quantity  of  water  than  is  used  for  the 
normal  developer,  and  advises  a rapid  development.  I have 
done  good  work  by  this  method,  but  many  makes  of  plates 
will  not  stand  forcing  at  the  outset.  A safer  plan  is  to  be- 
gin with  a weakened  developer,  giving  the  plate  a prelimi- 
nary soaking  for  two  or  three  minutes  in  a dilute  alkaline 
solution  made  by  diluting  the  usual  ten  per  cent,  stock  so- 
lution with  twice  its  bulk  of  water. 

It  is  important  that  the  details  be  obtained  before  suffi- 
cient printing  density  is  had,  and  the  preliminary  alkaline 
treatment  helps  towards  this.  A very  safe  method  is  to 


55 


56 


Development  of  Dry  Plates. 


keep  the  alkaline  and  reducing  solutions  in  separate  trays, 
changing  the  plate  from  one  to  the  other  as  may  be  neces- 
sary. In  this  way  the  operator  has  more  control  of  the 
process  and  is  better  able  to  treat  his  subject  intelligently. 
As  a general  rule  it  is  safe  to  say  that  the  alkaline  treat- 
ment should  predominate  at  the  beginning  at  least,  and  that 
density  should  be  sought  for  only  well  towards  the  end  of 
development. 

Any  of  the  formulae  already  given  will  serve  the  present 
purpose,  bearing  in  mind  the  special  directions  given  for  the 
treatment  of  under-exposed  plates.  Above  all  things  avoid 
being  in  a hurry.  It  may  take  an  hour  to  develop  a shutter 
exposure,  but  I am  seldom  longer  than  twenty  minutes 
about  it.  The  development  must  be  carried  further  than 
with  longer  exposures.  Quick  plates  feebly  light-impressed 
lose  much  of  their  density  in  the  fixing  bath.  The  image 
should  show  strongly  on  the  back. 

The  eikonogen  developer  seems  to  possess  a better  capac- 
ity for  rounding  out  an  instantaneous  exposure  than  either 
pyro  or  hydrochinon,  and  there  is  less  likelihood  of  stain. 

Development  of  Films.— Very  little  need  be  said  on  the 
development  of  the  film  negatives,  which  seem  likely  to  play  . 
an  important  part  in  the  photography  of  the  future.  They 
are  coated  with  the  same  emulsion  used  on  glass,  and  the 
only  modifications  are  those  made  necessary  by  the  uncom- 
fortable tendency  of  the  films  to  curl  up  in  the  bath,  a diffi- 
culty more  apparent  with  the  thin  Eastman  film  than  with 
those  which  have  a thicker  base  of  celluloid.  In  the  case 
of  the  former  I have  found  it  a fairly  good  plan  to  soak  the 
film  for  a short  time  in  clean  water  to  which  a slight  trace 
of  glycerine  has  been  added,  or  to  add  a modicum  of  glyc- 
erine to  the  developer.  The  use  of  glycerine  is  not,  how- 


Development  of  Dry  Plates. 


57 


ever,  to  be  advised  indiscriminately.  In  damp  weather  it 
will  not  be  needed,  and  on  the  whole  it  is  better  to  endure 
the  ills  of  curled  films  than  to  make  use  of  a substance 
likely  to  complicate  the  drying. 

Any  developer  that  will  work  satisfactorily  with  films  on 
glass  will  work  equally  well  with  celluloid  films.  After  fix- 
ing and  washing,  the  films  should  be  pinned  by  the  corners 
to  boards  in  order  that  the  tendency  to  curl  may  be  dimin- 
ished. If  after  drying,  they  curl  badly,  they  should  be 
wound  tightly  about  a round  stick  with  the  films  out  and 
left  for  an  hour  or  two  to  straighten. 

So  far  as  my  experience  extends,  the  greatest  difficulty 
with  thin  films  at  least  comes  in  the  printing  frames,  when 
the  heat  of  the  sun  is  apt  to  aggravate  the  tendency  to 
curl. 

Development  of  Lantern  Slides. — The  prime  essential 
to  a thoroughly  good  slide  is  sufficient  clearness  in  the  high 
lights  to  allow  most  of  the  light  to  pass  through,  and  not 
sufficient  density  in  the  shadows  to  offer  too  great  an  ob- 
struction to  the  passage  of  the  light.  • Most  slides  made  by 
amateurs  err  in  both  these  particulars.  They  are  too  dense 
in  the  shadows  and  too  transparent  in  the  lights.  Abso- 
lutely clear  glass  is  not  what  is  wanted  in  the  perfect  slide, 
but  just  the  degree  of  depth  of  deposit  which  will  give  at- 
mosphere to  the  projected  image.  I am  speaking  now  of 
slides  of  natural  scenery.  For  buildings,  reproductions  of 
drawings,  plans,  etc.,  the  shadows  should  be  dense  and  the 
lights  transparent.  But  the  snow  effect  so  often  seen  in 
slides  with  summer  foliage,  owing  to  the  excessive  clearness 
of  the  high  lights  is  neither  pleasing  nor  truthful.  I do  not 
believe  that  the  perfect  slide  can  be  made  on  the  gelatine 
dry  plate,  and  I would  strongly  advise  all  amateurs  who 


58 


Development  of  Dry  Plates. 


“ go  in  ” largely  for  slide  making  to  book  themselves  up  in 
the  wet  collodion  or  tannin  processes,  either  of  which  are 
vastly  more  economical  and  give  better  results  than  the 
best  gelatine  lantern  slide  plates.  But  as  I know  that  few 
will  take  this  trouble,  I give  one  or  two  formulae  which 
I have  found  to  be  reliable.  But  before  doing,  I wish  to 
say  a word  about  the  exposure.  Whether  made  by  contact 
printing  or  by  reduction  in  the  camera,  a full  exposure 
should  be  given  if  the  best  results  are  desired.  A lantern 
slide  which  has  been  forced  in  development  to  bring  out 
details  which  should  have  come  out  easily,  is  rarely  such 
as  one  would  care  to  exhibit.  In  order  to  give  clean  effects 
it  is  usually  advisable  to  add  a considerable  proportion  of 
bromide  to  the  developer,  and  this  addition  necessitates  a 
full  exposure,  which  must  not,  however,  be  prolonged  to 
the  fogging  point. 

The  ferrous-oxalate  developer  has  long  been  a favorite 
with  dry-plate  slide  makers,  on  account  of  its  simplicity  and 
cleanliness. 

Those  who  like  strong  and  vigorous  blacks  will  find  the 


following  formula  a good  one  : 

A.  Oxalate  of  potash, 8 ounces. 

Water, 30  “ 

Citric  acid, 60  grains. 

B.  Sulphate  of  iron, 4 ounces. 

Sulphuric  acid,  8 drops. 

Water, 32  ounces. 


For  the  developer  add  1 ounce  of  B to  3 of  A,  and  ^ 
ounce  of  water,  and  5 to  10  drops  of  the  usual  bromide 
solution. 

Allow  development  to  proceed  until  the  shadows  are 
strong  and  the  image  visible  on  the  back.  Then  wash  and 


Development  of  Dry  Plates.  ♦ 59 

fix.  Wash  for  half  an  hour  and  immerse  for  five  minutes  in 


Water, 36  ounces, 

Pulverized  alum, 3 “ 

Citric  acid, \ ounce, 


to  harden  the  film  and  clear  the  image. 

Hydrochinon,  pyrogallol  or  eikonogen  will  give  equally 
as  good,  if  not  better  results.  The  following  formulae  are 
known  to  be  reliable  : 

HYDROCHINON. 


A.  Sulphite  of  Soda  (crystals) 400  grains, 

Water, 6 ounces, 


dissolve  and  filter,  and  add 


Hydrochinon, 120  grains, 

B.  Carbonate  of  potassium,  ......  240  “ 

Water, 6 ounces, 


dissolve  and  filter. 

Developer. — 1 ounce  each  of  A and  B,  and  2 ounces 
of  water.  Bromide  if  needed  to  produce  clean  work. 

EIKONOGEN. 


A.  Sulphite  of  soda  (crystals),  .....  240  grains, 

Water, 8 ounces, 

dissolve,  filter,  and  add 

Eikonogen, 20  grains, 

B.  Carbonate  of  potash, 32  “ 

Water, 1 ounce. 


Developer. — 2 ounces  of  A and  1 dram  of  B. 


6o 


Development  of  Dry  Plates. 


PYROGALLOL. 


A.  Carbonate  of  soda  (crystals), i ounce. 

Water, 8 “ 

B.  Sulphite  of  soda  (crystals), i “ 

Water, .8  “ 

Pyrogallol, 2 drams. 


Developer. — Equal  parts  of  A and  B.  Restrain  with 
bromide  if  necessary. 

The  development  of  lantern  slides  should  be  continued 
until  the  image  is  clear  and  distinct  and  seemingly  more 
dense  than  is  necessary,  but  for  clean  work  it  is  essential 
that  the  development  be  stopped  as  soon  as  the  edges  of 
the  plate  show  signs  of  darkening,  or  even  before.  Other- 
wise the  high  lights  will  be  too  strongly  veiled.  Cleanliness 
is  another  essential  point.  It  is  best  to  have  a separate  set 
of  trays  for  developing  slides.  The  hypo  solution  should  be 
freshly  mixed,  and  for  slides  it  need  not  be  stronger  than  1 
to  10.  The  acid  fixing  bath  is  to  be  recommended. 


CHAP  TER  XI. 


fixing  aNd  Washing. 

T^IXING.  — The  process  of  fixing  is  necessary  in  order 
A to  dissolve  out  all  the  unreduced  silver  which  is  still 
sensitive  to  light,  and  therefore  a cause  of  fading  or  dark- 
ening if  the  unfixed  plate  be  exposed  to  the  action  of  light. 

After  development,  the  film  contains  both  metallic  silver 
and  unaltered  bromide  of  silver  ; both  of  these  salts  must 
be  removed  by  a suitable  solvent  in  order  to  render  the 
negative  transparent  and  permanent.  The  salt  most  com- 
monly employed  for  this  purpose  is  the  hyposulphite  or 
thiosulphite  of  sodium.  When  a negative  is  immersed  in  a 
solution  of  this  salt  a double  hyposulphite  of  silver  and 
sodium  is  formed.  The  first  is  readily  soluble  both  in  a 
solution  of  hypo  and  in  water,  while  the  second  is  insoluble 
in  water  and  only  slowly  soluble  in  hypo  solutions.  Hence, 
the  necessity  for  a prolonged  immersion  in  the  fixing  bath 
to  insure  the  complete  solution  of  the  salt,  the  presence  of 
which  in  the  negative  would  cause  its  speedy  destruction. 
The  negative  should  be  left  in  the  bath  at  least  five  minutes 
after  the  whitish  color  has  disappeared. 

The  degree  of  concentration  of  the  hypo  solution  is  not 
of  special  importance,  except  so  far  as  it  affects  the  speed 
of  the  solving  action.  A dilute  solution  will  fix,  but  only 
slowly.  The  proportion  of  one  to  five  is  about  right.  Until 
quite  recently  a plain  hypo  solution  has  been  most  common- 
ly employed,  the  addition  of  alum  to  harden  the  film  and 

61 


62 


Development  of  Dry  Plates. 


prevent  frilling  not  being  advisable  on  account  of  the  dan- 
ger of  the  formation  of  a sulphur  compound.  But  within  a 
short  time  acid  solutions  have  been  recommended,  on  account 
of  the  clearing  and  hardening  action  which  such  a solution 
has  on  the  gelatine  film  and  the  greater  permanency  thus 
given  to  the  bath.  A solution  of  hyposulphite  undergoes  a 
change  even  when  kept  from  atmospheric  influences.  Sul- 
phur is  deposited  and  sulphite  of  sodium  formed.  The 
presence  of  the  latter  salt  is  not  injurious,  since  it  is  itself 
a fixing  agent,  but  tfie  presence  of  sulphur  is  likely  to  work 
injury  to  the  negative. 

One  of  the  latest  and  best  formulae  for  the  fixing  bath 


is  Cramer’s,  as  follows  : 

Water,  . i , quart, 

Sulphite  of  soda  (crystals)  . . . . .4  ounces, 

Dissolve,  and  add 

Sulphuric  acid ^ ounce, 

Chrome  alum  (powdered), 3 ounces, 

Dissolve  and  pour  into  a solution  of 

Hypo, 2 pounds, 

Water,  3 quarts. 


This  bath  remains  clear  even  with  frequent  use;  it  does 
not  discolor  the  film,  and  it  has  a hardening  effect. 

Another  equally  good  bath  is  made  by  the  addition  of 
one  ounce  of  acid-sulphite  of  sodium,  a new  chemical,  to 
each  pint  of  hypo  solution.  In  this  bath,  which  remains 
clear  after  long  use,  fixation  is  very  rapid.  The  only  pre- 
caution necessary  is  to  keep  the  bath  distinctly  acid  at  all 
times  by  the  occasional  addition  of  fresh  acid-sulphite 
solution. 


Development  of  Dry  Plates.  63 

I would  strongly  advise  the  use  of  a grooved  tank  or  a 
triangular  trough  for  the  fixing  bath  in  place  of  the  time- 
honored  tray,  which  allows  all  the  impurities  present  in  the 
bath  to  settle  on  the  film  to  its  detriment.  In  a tank  the 
negatives  stand  up  in  the  bath  and  the  impurities  do  not  at- 
tach themselves  to  the  films.  In  a trough  they  are  fixed 
with  the  films  down. 

Since  the  formation  of  the  double  insoluble  hyposulphite 
is  promoted  by  the  action  of  light,  the  fixing  should  be 
done  in  the  developing  room,  but  extreme  care  must  be 
taken  to  keep  the  fixing  solution  from  the  developing  trays. 

The  number  of  plates  which  can  safely  be  fixed  in  a 
single  solution  of  hyposulphite  has  its  limits.  It  is  limited 
by  the  production  of  the  double  salt.  Fifteen  grains  of 
bromide  of  silver  require  about  seven  grains  of  hyposul- 
phite to  form  the  double  salt.  The  average  whole  plate 
contains  not  far  ‘from  fifteen  grains  of  bromide  of  silver, 
and  seven  grains  of  hyposulphite  are  required  to  form  the 
double  salt.  If  then  we  have  twenty  ounces  of  bath  con- 
taining four  ounces  of  hyposulphite,  we  can  theoretically 
fix  at  least  220  whole  plates  in  it.  But  since  an  excess  of 
hyposulphite  is  necessary  in  order  to  dissolve  the  double 
salt  it  is  not  safe  to  fix  more  than  half  that  number.  The 
cost  of  the  hyposulphite  is  low  enough  to  warrant  a little 
prodigality  in  its  use. 

In  order  to  make  sure  of  perfect  fixation,  the  negative 
must  be  left  in  the  fixing  bath  for  some  time  after  all  white- 
ness has  disappeared  from  the  back.  It  is  also  advisable  to 
place  the  plate  for  a short  time  in  a second  fixing  bath 
freshly  mixed. 

Washing. — The  elimination  of  the  last  traces  of  hypo 
from  the  film  is  a matter  of  no  little  difficulty.  Unless  the 


64 


Development  of  Dry  Plates. 


fixing  agent  is  entirely  removed,  the  negative  will  soon  be 
made  useless  for  printing  by  the  formation  of  the  unstable 
hyposulphurous  acid,  which  rapidly  decomposes  into  sulphur 
and  sulphurous  acid,  a decomposition  which  produces  the 
yellowing  of  the  film  which  is  so  frequently  met  with  in 
negatives  which  have  been  printed  from  a few  times.  For 
rapid  and  thorough  washing  nothing  is  better  than  a 
grooved  washing  box  and  an  abundance  of  running  water. 
Two  or  three  hours  of  this  treatment  will  effectually  remove 
the  hypo.  Where  running  water  cannot  be  had  the  plates 
may  be  washed  in  a tray  by  frequently  changing  the  water. 
Better  than  this  is  a wooden  trough  in  which  the  negatives 
can  be  placed  with  the  films  down.  The  water  must  be  fre- 
quently changed.  Still  another  good  method  is  to  mount  a 
wooden  tank  at  the  end  of  a slanting  board  of  suitable 
length  and  width.  A small  short  pipe  is  inserted  at  the  bot- 
tom of  the  tank,  and  another  longer  piece  is  soldered  at 
right  angles  to  it.  This  pipe  is  closed  at  the  ends  and  has 
a number  of  fine  holes  pierced  along  the  front.  The  water 
is  thus  delivered  in  a fine  spray.  The  negatives  are  placed 
on  the  board,  the  tank  is  filled  with  water,  and  an  hour’s 
washing  will  leave  the  films  in  good  condition. 

Hypo  Eliminators. — Various  compounds  act  as  hypo 
eliminators  by  converting  it  into  a salt  which  is  easily 
washed  away,  or  whose  presence  in  the  film  is  not  in- 
jurious. They  should  be  used,  however,  only  after  the 
larger  portion  of  the  hypo  has  been  removed  by  washing. 
Alum  and  the  hypochlorites  have  been  recommended  as 
hypo  eliminators.  The  former,  while  unquestionably  a 
hypo  eliminator,  produces  a reaction  by  which  sulphur  is 
precipitated,  and  sulphur  is  nearly  as  difficult  to  eliminate 
as  hypo  itself. 


Development  of  Dry  Plates. 


65 


The  hypochlorites  are  free  from  this  objection.  Javelle 
water,  a compound  of  hypochlorite  and  chloride  of  potas- 
sium, is  a very  good  eliminator  of  hypo.  The  plate  is  im- 
mersed in  a bath  containing  fifteen  parts  of  Javelle  water 
to  one  hundred  parts  of  water,  where  it  is  allowed  to  re- 
main for  five  minutes,  after  which  it  is  washed  for  ten  or 
fifteen  minutes.  The  theory  of  the  reaction  is  that  the 
chlorine  of  the  hypochlorite  decomposes  the  water,  forming 
hydrochloric  acid  and  oxygen.  The  oxygen  oxidizes  the 
hyposulphite  and  converts  it  into  bisulphate  of  potassium, 
a salt  which,  being  readily  soluble  in  water,  is  easily  washed 
out. 

Belitzsky’s  hypochlorite  of  zinc  eliminator  is,  perhaps, 
better  than  Javelle  water.  This  is  made  by  dissolving  300 
grains  of  chloride  of  lime  in  one  quart  of  water,  six  hundred 
grains  of  zinc  dissolved  in  twice  its  weight  of  water.  The 
mixture  is  shaken  and  allowed  to  settle.  The  clear  portion 
is  decanted  for  use,  one  part  being  added  to  sixty  parts  of 
water  to  form  the  eliminator. 

Test  for  Hypo. — If  the  operator  wishes  to  make  sure 
that  the  last  traces  of  hypo  have  been  removed,  he  must 
test  the  last  wash  water  for  traces  of  the  salt.  Iodide  of 
starch  forms  a very  delicate  test  for  hypo. 

This  is  prepared  by  dissolving  a small  quantity  of  starch 
in  ten  times  its  weight  of  water,  and  boiling  until  the 
solution  .be  clear.  A few  drops  of  a saturated  alcoholic 
solution  of  iodine  are  then  added,  which  forms  the  blue 
iodide  of  starch.  Two  drops  of  this  are  sufficient  to  impart 
a bluish  tinge  to  distilled  water.  But  if  any  traces  of  hypo 
are  present  the  blue  will  not  appear. 

On  the  Use  of  Alum. — Alum,  owing  to  its  hardening 
action  on  films  of  gelatine,  has  often  been  recommended  as 


66 


Development  of  Dry  Plates. 


a useful  addition  to  the  fixing  bath  to  prevent  frilling,  but 
this  addition  is  to  be  deprecated  as  of  little  value  and  liable 
to  injure  the  film.  The  sulphate  of  aluminium  contained 
in  the  alum  forms  with  hypo  a precipitate  of  alumnium  and 
sulphur  which  is  insoluble  and  detracts  from  the  clearness 
of  the  negative.  For  this  reason,  I cannot  advise  the  use  of 
alum  in  connection  with  the  fixing  bath. 

Another  purpose  for  which  alum  has  been  recommended 
is  to  remove  the  yellow  color  sometimes  produced  by  pyro- 
gallol.  This  practice  is  not  free  from  danger  unless  a ver- 
tical tank  is  used. 

Most  water  contains  carbonate  of  chalk,  a substance  which 
in  connection  with  sulphate  of  aluminium  forms  carbonic 
acid,  sulphate  of  chalk  and  the  insoluble  sub-sulphate  of 
aluminium,  which  is  precipitated  on  the  film,  bearing  with 
it  any  impurities  in  suspension  in  the  bath.  In  order  to 
avoid  this  precipitation  on  the  film,  a vertical  tank  should 
be  used. 

The  alum  bath,  properly  used,  has  undoubtedly  great 
value  in  promoting  the  preservation  of  the  negative,  by 
rendering  the  gelatine  inert  to  the  action  of  moisture. 
After  a thorough  removal  of  the  hypo  it  is  always  well  to 
immerse  the  plate  for  a short  time  in  a saturated  solution 
of  alum  and  then  to  wash  for  a few  moments. 

Clearing  Solution. — The  yellow  color  due  to  the  use  of 
pyrogallol  may  be  removed  by  immersing  the  plate,  after 
fixing  and  washing,  in  the  following  solution: 


Saturated  solution  of  alum,  . . • . . .32  ounces. 

Sulphuric  acid,  ^ ounce. 


CHAPTER  XII. 


intensification  ANd  reduction. 

T NTENSIFICATION.  — Occasionally,  either  by  reason  of 
^ under-  or  over-exposure,  or  from  insufficient  develop- 
ment, the  negative  lacks  the  necessary  printing  strength. 
The  contrasts  are  too  feeble  to  give  strong  prints. 

This  weakness  may  be  overcome  by  the  process  known  as 
intensification,  which  consists  in  substituting  a more  opaque 
deposit  for  the  deposit  of  silver.  By  this  means  the  high 
lights  become  more  intense  and  the  negative  more  vigorous. 
The  possibility  of  successful  intensification  depends  upon 
the  fact  that  the  intensifying  solutions  act  upon  the  different 
parts  of  the  negative  in  proportion  to  the  amount  of  silver 
contained  in  them.  The  high  lights,  having  a denser  de- 
posit of  silver,  are  more  strongly  acted  upon  than  the  shad- 
ows where  the  silver  deposit  is  less  dense.  In  this  way  the 
contrasts  are  heightened. 

Intensification  may  be  partial  or  complete,  local  or  gen- 
eral. Partial,  when  only  a part  of  the  reduced  silver  is 
acted  upon;  complete,  when  the  intensifier  is  allowed  to  act 
until  it  has  penetrated  through  the  film;  local,  when  only  a. 
part  of  the  film  is  intensified;  general,  when  the  whole  sur- 
face is  acted  on.  Partial  intensification  is  to  be  resorted  to 
when  the  negative  lacks  only  a slight  degree  of  density;  its 
effect  is  to  increase  the  contrast  between  the  half-tones 
without  appreciably  increasing  the  general  contrast  between 
the  half-tones  and  the  high  lights.  -Complete  intensification 

67 


68  Development  of  Dry  Plates. 

is  necessary  for  thin,  monotonous  negatives.  The  essential 
difference  between  partial  and  complete  intensification  is 
simply  one  of  the  length  of  time  the  intensifier  is  allowed  to 
act. 

It  must  be  remembered  that  intensification  does  not  pro- 
duce detail  ; it  simply  heightens  contrast  and  increases 
density.  There  is  no  more  detail  in  a negative  after  inten- 
sification than  before.  The  detail  may  be  more  distinctly 
visible  owing  to  the  greater  strength  imparted  to  it,  but  the 
detail  must  be  in  the  negative  before  intensification. 

Another  point  in  connection  with  intensification  is  the 
necessity  of  a thorough  elimination  of  the  hypo  before  any 
attempt  is  made  to  strengthen  the  negative.  If  this  point 
is  not  attended  to  the  film  will  inevitably  be  stained. 

One  of  the  most  common  methods  of  intensification  is  a 
preliminary  treatment  with  bichloride  of  mercury,  followed 
by  copious  washing  and  a subsequent  treatment  of  the  mod- 
ified silver  with  ammonia  or  sulphite  of  soda.  In  this  case 
the  mercuric  chloride  is  converted  into  mercurous  chloride 
by  the  loss  of  half  its  chloride  which  acts  upon  the  silver  of 
the.  film  and  converts  it  into  chloride  of  silver.  Both  mer- 
curous and  argentic  chlorids  are  colorless,  hence  the  action 
of  the  bath  whitens  the  film.  After  a thorough  washing, 
the  film  is  treated  with  a dilute  solution  of  ammonia. 

In  this  bath  a double  reaction  takes  place.  The  ammonia 
dissolves  the  chloride  of  silver  and  forms  an  ammonia-mer- 
curic compound  with  the  chloride  of  mercury.  This  com- 
pound is  an  intense  black,  and  taking  the  place  of  the  silver 
in  the  film,  it  acts  as  an  intensifier. 

The  bichloride  of  mercury  bath  should  be  made  by  dis- 
solving one  part  of  the  mercury  in  twenty  parts  of  hot 
water. 


Development  of  Dry  Plates.  69 

The  well  washed  plate  is  placed  in  a tray  and  covered 
with  the  solution.  If  partial  intensification  is  all  that  is  de- 
sired, the  action  of  the  bath  is  stopped  before  the  film  is 
whitened  through  to  the  glass.  Where  complete  intensifica- 
tion is  necessary,  the  film  must  be  whitened  through  its  en- 
tire thickness.  After  washing  for  fifteen  minutes  in  running 
water,  the  plate  is  placed  in  a solution  of  ammonia  diluted 
with  twenty  times  its*  bulk  of  water.  The  film  quickly 
blackens,  and  when  the  whiteness  has  entirely  disappeared, 
it  only  remains  to  wash  the  plate  thoroughly.  The  tray 
should  be  rocked  to  insure  an  even  action. 

If  the  negatives  are  thoroughly  washed  after  fixing  and 
after  the  mercury  treatment,  there  is  no  reason  to  suspect 
the  permanency  of  the  intensified  film. 

A ten  per  cent,  solution  of  sulphite  of  sodium  may  be 
substituted  for  the  ammonia  solution  of  the  preceding  for- 
mula, and  in  this,  case  the  washing  after  the  mercury  treat- 
ment need  not  be  so  thorough.  The  reaction  is  similar 
to  the  preceding,  the  sulphite  dissolves  the  chloride  of 
silver  and  reduces  the  mercurous  chloride  to  the  metallic 
state. 

A modification  of  the  above  method  is  to  treat  the  plate 
after  whitening  with  mercury  with  the  ferrous-oxalate  de- 
veloper. In  this  case  both  the  chlorides  of  silver  and  mer- 
cury are  reduced  to  the  metallic  state.  If  the  negative  is 
not  sufficiently  intense  after  this  treatment,  the  film  may  be 
again  whitened  and  the  developer  applied  as  before.  Other 
methods  of  intensification  will  be  found  in  the  tables  of 
formulae. 

Local  Intensification. — It  often  happens  that  certain 
portions  only  of  the  negative  are  too  thin  to  print  well. 
This  is  most  common  with  negatives  containing  deep 


70 


Development  of  Dry  Plates. 


shadows  when  the  time  of  exposure  was  not  sufficient  to 
bring  out  detail  with  the  proper  degree  of  density. 

In  this  case,  local  intensification  may  be  resorted  to.  The 
only  absolutely  certain  method,' in  my  experience,  is  the 
application,  with  a soft  brush,  of  Hall’s  Intensifier  to  the 
parts  to  be  intensified.  This  will  strengthen  the  detail.  To 
lighten  up  deep  shadows  and  prevent  them  from  printing 
too  deeply,  indigo  blue  moistened  with  gum  water  may  be 
applied  to  the  back  of  the  negative  with  the  finger. 

In  inexperienced  hands  intensification  is  rarely  success- 
ful, in  most  cases  producing  spots  and  stains  which  ruin  the 
negative.  It  is  always  better  to  make  a new  negative,  if 
possible,  or  to  over-develop  and  then  reduce. 

Reduction  of  Negatives. — There  are  two  distinct  cases 
in  which  it  is  advisable  to  reduce  the  density  of  a negative: 
i,  those  cases  in  which  the  general  density  is  so  great  as  to 
make  the  negatives  abnormally  slow  printers  ; and,  2,  those 
cases  in  which  by  reason  of  insufficient  exposure,  and  con- 
sequent prolonged  development  to  bring  out  detail,  the 
contrasts  are  too  strong  and  the  density  of  the  high  lights 
too  great. 

In  the  first  case  it  is  necessary  to  dissolve  a portion  of 
the  reduced  silver  without  altering  the  tone  gradation.  In 
the  second  case  only  the  high  lights  should  be  reduced, 
leaving  the  shadows  unaffected.  This  may  be  called  the 
method  of  local  reduction,  and  is  best  effected  by  applying 
the  reducer  given  below  to  the  parts  which  it  is  desired  to 
reduce  with  a soft  brush. 

Farmer’s  ferricyanide  and  hypo  reducer  is  one  of  the  most 
reliable.  The  negative  is  immersed  for  a few  moments  in  a 
one  to  two  hypo  solution.  A few  drops  of  a one  to  ten  so- 
lution of  ferricyanide  of  potassium  solution  are  added,  and 


Development  of  Dry  Plates. 


7i 


the  progress  of  the  reduction  carefully  watched.  If  the  ac- 
tion is  not  sufficiently  rapid  more  of  the  ferricyanide  may 
*be  added.  When  the  negative  has  been  sufficiently  reduced, 
it  must  be  thoroughly  washed  to  reduce  the  hypo. 

For  local  reduction,  the  mixed  reducer  is  applied  with  a 
soft  brush,  but  the  operation  demands  great  delicacy  of 
touch. 

Dr.  Eder  recommends  a reduction  method,  which  consists 
in  converting  the  reduced  silver  into  chloride  of  silver,  and 
then  reducing  or  reconverting  the  chloride  into  the  metallic 
state.  By  this  method  the  half  tones  may  be  brought  into 
better  balance  with  the  high  lights.  The  method  is  as 
follows  : 

The  plate  is  immersed  for  a few  moments  in 

Water, 1 ounce.  N 

Bichloride  of  potassium,  ....  5 grains. 

Hydrochloric  acid,  5 drops. 

After  washing,  the  image  is  redeveloped  with  ferrous-ox- 

alate, then  fixed  and  washed  as  usual. 

In  order  to  reduce  a negative  which  has  been  made  too 
intense  by  the  mercury  intensification,  a dilute  solution  of 
cyanide  of  potassium  may  be  used,  but  as  this  is  a virulent 
poison  the  greatest  care  must  be  taken  in  its  use. 


CHAPTER  XIII. 


supplementary  Notes. 

CO  MUCH  of  the  quality  of  the  negative  depends  upon 
^ its  proper  development,  that  I am  not  willing  to  leave 
the  subject  without  a few  additional  remarks,  which  I 
trust  may  still  further  clarify  the  matter  and  help  to  make 
the  development  of  a negative  less  a matter  of  chance  and 
luck  and  more  of  scientific  accuracy. 

This  also  affords  an  opportunity  of  calling  attention  to  a 
new  ingredient  of  the  developer  which  has  been  introduced 
into  this  country  from  Germany,  and  which  my  experiments 
have  conclusively  proven  to  be  a valuable  addition  to  Mate- 
ria Photographica.  This  substance  is  a strong  solution  of 
the  acid-sulphite  of  sodium  which,  formed  in  the  solution 
when  sulphite  and  an  acid  were  added,  acted  as  a preserver. 
But  the  quantity  of  acid-sulphite  thus  formed  was  exceed- 
ingly small  as  compared  with  the  amount  of  sulphite  present. 
The  new  solution  contains  fifty  per  cent,  of  acid-sulphite  in 
solution,  and  twice  the  amount  of  the  preserving  element, 
sulphurous  oxide,  contained  in  ordinary  sulphite  of  soda 
crystals.  It  comes  in  the  form  of  a pale,  yellowish  liquid, 
with  a strong  smell  of  sulphurous  oxide  gas,  with  which  it  is 
saturated.  The  effect  of  its  addition  to  the  fixing  bath  is 
to  hasten  the  action  of  the  bath  and  to  prevent  its  dis- 
coloration. Negatives  fixed  in  this  modified  bath  are 
remarkably  clear  and  free  from  stain.  Added  to  the  devel- 
oper the  new  reagent  acts  as  a powerful  preserver  and 
diminishes  the  likelihood  of  stain  or  fog. 


72 


Development  of  Dry  Plates. 


73 


The  proper  proportions  for  the  fixing  bath  are  about  one 
ounce  of  the  acid-sulphite  solution  to  every  pint  of  bath, 
adding  more  as  the  bath  loses  its  acid  reaction. 

For  the  pyro  developer  one  drop  of  acid  sulphite  should 


be  used  for  each  grain  of  pyro;  a trifle  less  is  necessary  for 
eikonogen.  It  does  not  seem  to  give  good  results  with 

hydrochinone. 

The  following  formulae  were  recommended  in  Anthony’s 
Bulletin,  and  have  given  me  remarkably  good  results: 

A. — Pyrogallol, 

. . 1 ounce. 

Acid-sulphite, 

Water, 

B — Carbonate  of  soda  (crystals), 

. . 5 ounces. 

Water,  to  make 

Developei  : — Water,  i ounce ; A,  j to 

1 dram  ; B,  i|  to  2 drams. 

A. — Eikonogen  (finely  powdered), 

. . 1 dram. 

Acid- sulphite, 

. . 1 dram. 

Water,  to  make 

Dissolve  the  eikonogen  before  adding  the  acid-sulphite. 

B. — Carbonate  of  potassium  (dry), 

. . 3 ounces. 

Water, 

. . 10  ounces. 

Developer  : — A,  i ounce  ; B,  i to  2 drams. 

Lambert’s  Ammonia  Developer.— 

-In  the  British  Journal 

Year  Book  for  1890,  the  Rev.  F.  C.  Lambert  gives  a form- 
ula for  an  ammonia  developer,  with  tabulated  directions  for 
its  use,  which  is  well  worth  reproducing  here: 

P. — Sulphite  of  soda, 

. . ig-  ounces. 

Pyro, 

. . 1 ounce 

Citric  acid, 

Water,  to  make 

. . 6 ounces. 

B. — Bromide  of  potassium,  . . . 

. . ^ ounce. 

Water, 

. . 4 ounces. 

A. — Ammonia  (.880)  .... 

. . 1 ounce. 

Water,  to  make  ..... 

. . 4 ounces. 

74 


Development  of  Dry  Plates. 


The  table  gives  the  approximate  relative  proportions  of 
P.  B.  & A.  in  drops  for  four  ounces  of  developer.  The  table 
is  suggestive  only,  and  must  be  modified  to  suit  the  plate, 
subject  and  conditions  of  exposure. 


EXPOSURE. 

SUBJECT. 

P. 

B. 

A. 

( 

Strong  in  contrast 

10-20 

10-20 

IO-30 

Under < 

Normal  “ “ 

*0-40 

10-20 

30-40 

( 

Weak  “ “ 

J T 

40-50 

10-20 

40-60 

( 

Strong  in  contrast 

30-60 

30-60 

30-60 

Medium  -1 

Normal  “ “ 

60 

60 

60 

Weak  “ “ 

60-90 

6O-9O 

30-60 

( 

Strong  in  contrast 

60 

60 

10-20 

Over  

Normal  “ ‘ ( 

60-90 

60-QO 

20-30 

( 

i Weak  “ “ 

90-120 

90-120 

1 20-30 

The  careful  study  of  this  and  the  following  tables  will 
teach  the  thoughtful  experimenter  many  valuable  lessons 
in  development. 

M.  Londe  has  compiled  the  following  useful  tables  on  the 
modification  of  the  developer  : 

MODIFICATIONS  IN  DEVELOPMENT 


ACCORDING  TO  THE  RESULT  DESIRED. 


Result  Desired. 

Exposure. 

Modification*?. 

Method  of 
Development. 

Negative  with  strong 
contrasts. 

Short. 

Concentrated 

Bath. 

Bromide.  Rapid 
Development. 

Density, 
then  Detail. 

Soft,  harmonious  negative. 

Prolonged. 

Dilute  Bath. 

Trace  of  Bromide. 
Slow  Development. 
Detail, 

then  Density. 

MODIFICATION  OF  THE  DEVELOPER 


Development  of  D?y  Plates . 


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7 6 


Development  of  Dry  Plates. 


Development  with  Ammonia  Vapors. — Dry  plates  may 
be  developed  by  means  of  the  vapor  of  ammonia.  The  plates 
are  soaked  for  some  time  in  a normal  pyrogallol  solution 
and  then  exposed  to  the  ammonia  vapor.  This  is  best 
effected  by  pouring  a dilute  solution  of  ammonia  into  a tray 
and  holding  the  plate,  film  down,  a few  inches  above  the 
tray.  Care  must  be  taken  to  avoid  too  strong  a solution  of 
ammonia,  as  it  is  liable  to  produce  red  and  green  fog.  The 
greatest  advantage  of  this  method  is  its  adaptability  to  the 
local  development  of  those  parts  of  the  plate  which  show  a 
lack  of  detail  when  developed  by  the  usual  method.  For 
this  purpose  the  ammonia  should  be  kept  in  a bottle  provi- 
ded with  a small  tube.  Those  parts  of  the  plate  which  it 
is  desired  to  develop  further  are  held  over  the  tube  until 
the  details  are  out.  In  this  way  it  is  often  possible  to  bring 
out  detail  in  the  shadows,  but  there  is  more  or  less  of  un- 
certainty about  the  process. 

Development  in  Two  Solutions. — Some  operators  ad- 
vise the  use  of  two  solutions,  one  of  the  developer  proper 
and  the  other  of  the  alkali.  If  the  plate  has  been  over-ex- 
posed it  is  soaked  for  a short  time  in  a solution  of  pyrogal- 
lol or  other  reducing  agent,  and  afterwards  transferred  to 
a tray  containing  the  alkali.  This  will  bring  out  the  details. 
If  density  is  lacking  the  plate  is  again  placed  in  the  first 
tray.  For  under-exposures  the  process  is  reversed  and  the 
plate  is  placed  in  the  alkali  solution  first. 

Intentional  Over-Exposure. — One  of  the  safest  rules 
for  exposure  is  to  give  the  plate  as  long  an  exposure  as  it 
will  bear  without  fogging.  By  this  means  one  is  sure  of 
detail,  and  in  general  a better  balanced  negative.  Even 
with  extremely  rapid  plates  of  good  make  considerable  lati- 
tude of  exposure  is  possible,  if  the  necessary  conditions  of 


Development  of  Dry  Plates , 


77 


development  are  understood  and  met.  With  a given  de- 
velopment there  is  for  each  class  of  subjects  a time  of  ex- 
posure which  may  be  called  normal  by  which  is  meant  an 
exposure  which  will  give  the  best  results  with  the  given  de- 
veloper. But  even  with  long  practice  it  is  far  from  easy  to 
determine  the  exact  time  of  this  normal  exposure.  If  the 
exposure  has  been  too  short,  there  will  be  a lack  of  detail 
in  the  finished  negative.  If  an  over-exposure  has  been 
given,  there  will  be  plenty  of  detail,  but  a lack  of  density, 
and  perhaps  fog. 

There  is  no  method  by  which  details  are  brought  out  on 
a plate  which  has  not  received  sufficient  exposure  to  im- 
press them  on  the  sensitive  surface,  but  it  is  possible,  as 
has  been  shown,  to  modify  the  developer  in  such  a way  as 
to  overcome  the  effects  of  over-exposure.  For  this  reason 
it  is  always  best  to  give  as  long  an  exposure  as  the  plate 
will  bear  without  fogging,  and  to  modify  the  developer  ac- 
cordingly. In  this  way  one  is  sure  of  the  details  in  the 
shadows,  and  a little  practice  will  give  the  necessary  knowl- 
edge of  the  amount  of  over-exposure  allowable  with  any 
special  plate.  , 

Local  Development  by  Brushing. — A ve^  effective 
method  of  local  development  is  to  apply  strong  solutions 
to  the  portions  which  it  is  desired  to  force  by  means  of  small 
camels-hair  brushes.  The  brush  dipped  in  the  alkali  so- 
lution and  applied  to  the  plate  will  assist  in  bringing  out 
detail  which  would  otherwise  be  lacking.  The  reducing 
solution  may  be  applied  in  the  same  way  to  confer  density 
on  parts  which  develop  too  thin. 

The  Influence  of  Temperature  on  Development. — 
Heat  is  a great  promoter  of  chemical  action.  A cold  de- 
veloper will  develop  slowly  and  a warm  one  quickly,  often 


7» 


Development  of  Dry  Plates. 


with  lack  .of  density.  The  proper  temperature  for  the  de- 
veloper is  between  60  and  70  degrees.  This  temperature 
should  be  maintained  by  the  use  of  warm  water  in  winter 
and  ice  in  summer. 

If  a plate  develops  poorly  in  a solution  at  the  above  tem- 
perature, the  addition  of  a little  warm  water  will  often  help 
matters. 

Saturated  Solutions. — The  use  of  saturated  solutions 
is  to  be  deprecated  on  account  of  the  difficulty  of  obtaining  a 
solution  of  standard  strength.  If  a salt  is  dissolved  to  sat- 
uration in  hot  water  a certain  proportion  of  it  will  crystallize 
out  when  the  water  cools.  In  winter  the  strength  of  a 
saturated  solution  is  less  than  in  summer.  The  better  plan 
is  to  dissolve  a certain  number  of  parts  in  a sufficient  num- 
ber of  parts  of  water  to  keep  the  solution  well  within  the 
saturation  point.  In  this  way  one  is  always  sure  of  having 
a solution  of  standard  strength  at  any  temperature. 


FORMULAS 


DEVELOPERS. 

beach’s. 


A.  Warm  distilled  water, 2 ounces. 

Sulphite  of  soda  (crystals), 2 ounces. 

dissolve,  and  when  cold  add 

Sulphurous  acid, 2 ounces. 

Pyrogallol, ^ ounce. 

B.  1 Water, 4 ounces. 

Carbonate  of  potash, 3 ounces. 

2 Water, 3 ounces. 


Sulphite  of  soda  (crystals) 2 ounces. 

i and  2 are  combined.  For  shutter  exposures  take  3 
ounces  of  water,  ounce  of  A and  3 drams  of  B,  increasing 
the  latter  to  5 drams  if  the  image  hangs  back. 

For  over-exposures  take  3 ounces  of  water,  3 drams  of  A 
and  i dram  of  B,  adding  more  if  necessary.  Bromide  may 
be  used  to  restrain. 

PHOTO  TIMES  SODA  DEVELOPER. 


A.  Pyrogallol 1 ounce. 

Sulphite  of  soda  (crystals), 4 ounces. 

Sulphurous  acid, 4 ounces. 

Water, 10  ounces. 

B.  Carbonate  of  soda  (crystals),  . . . . 1 ounce. 

Sulphite  of  soda  (crystals), i£  drams. 

Water, 16  ounces. 


Developer  : 1 dram  of  A to  1 ounce  of  B.  For  under- 
exposures, increase  the  quantity  of  B ; for  over-exposures 
restrain  with  bromide  of  potassium  1 to  10. 


79 


8o 


Development  of  Dry  Plates. 


PHOTO  TIMES  POTASH  DEVELOPER. 


A.  Pyrogallol, i ounce. 

Sulphite  of  soda  (crystals), 4 ounces. 

Sulphurous  acid, 4 ounces. 

Water, 10  ounces. 

B.  Carbonate  of  potash, 3 ounces. 

Carbonate  of  soda  (granular)  . . . . 1 dram. 

Water,  10  ounces. 


Developer  : 1 ounce  of  water,  1 dram  each  of  A and  B. 
Accelerate  with  B.  Restrain  with  bromide  of  potash  1 
to  10. 

Cramer’s  carbonate  of  soda  developer. 


A.  Sulphite  of  sodium, 6 ounces. 

Carbonate  of  soda  (crystals),  ....  1^  ounces. 

Water, 64  ounces. 

B.  Distilled  water,  6 ounces. 

Sulphuric  acid, - 15  drops. 

Sulphite  of  soda  (crystals)  .....  1 dram. 

Pyrogallol, 1 ounce. 


Developer:  In  cold  weather  take  8 ounces  of  A,  and  2 
to  5 drams  of  B.  Keep  at  70  degrees. 

In  summer  take  6 ounces  of  water.  4 ounces  of  A and  2 
to  4 drams  of  B.  Keep  at  60  degrees. 

HARVARD  PYRO  DEVELOPER. 


A.  Distilled  water, 12  ounces. 

Sulphite  of  soda  (crystals),  .....  2 ounces. 

Citric  acid,  60  grains. 

Bromide  of  ammonium,  . . . - • .25  grains. 

Pyrogallol, 1 ounce. 

Dissolve  separately,  mix  in  order  given  and  filter. 

B.  Distilled  water, . .12  ounces. 

Sulphite  of  soda,  2 ounces. 

Carbonate  of  potash,  ....  4 ounces. 


Development  of  Dry  Plates.  81 

Developer  : A,  i dram  ; B,  i dram  ; water,  2 ounces. 
For  detail,  add  more  water  ; for  contrast,  increase  the 
amount  of  A ; for  density  use  more  of  A and  B.  For  in- 
stantaneous exposures  use  double  the  quantity  of  water  to 
begin  with.  When  development  is  partly  completed,  pour 
off  the  solution  and  finish  with  the  normal  developer. 

eder’s  one  solution  pyro  developer. 

Sulphite  of  soda  (crystals), 5 drams. 

Carbonate  of  soda  (crystals),  ....  2^  drams. 

Dissolve  in  2 ounces  of  boiled  distilled  water,  and  when 
cool  add  forty-six  grains  of  pyrogallol.  Keep  in  well  stop- 
pered bottles,  and  dilute  with  five  times  the  bulk  of  water 
for  use. 

cramer’s  hydrochinon  developer. 


A.  Sulphite  of  soda  (crystals),  ....  480  grains. 

Phosphate  of  soda, 160  grains. 

Water, 8 ounces. 

Dissolve,  filter,  and  add 

Hydrochinon, 100  grains. 

B.  Carbonate  of  soda  (crystals),  . . . 480  grains. 

Phosphate  of  soda, 160  grains. 

Water, 8 ounces. 

Developer.  — Equal  parts  of  A.  and  B. 


CHAUTAUQUA  HYDROCHINON  DEVELOPER. 


A.  Hydrochinon, ^ ounce. 

Sulphite  of  soda  (granular),  1 ounce. 

Meta-bisulphite  of  potassium,  . . 30  grains. 

Water, 16  ounces. 

B.  Carbonate  of  potash, lj?  ounces. 

Water, 16  ounces. 

Developer.  — Equal  parts  of  A and  B. 


82 


Development  of  Dry  Plates . 


EIKONOGEN  DEVELOPER. 


A.  Sulphite  of  soda  (crystals),  ....  4 ounces. 

Distilled  water, 60  ounces. 

Dissolve  and  add 

Eikonogen, 1 ounce. 

B.  Carbonate  of  soda  (crystals),  ...  3 ounces. 

Distilled  water,  . 20  ounces. 

Developer.  — 3 parts  of  A and  1 part  of  B. 

ONE  SOLUTION  EIKONOGEN  DEVELOPER. 
Sulphite  of  soda  (crystals),  ....  8 ounces. 

Carbonate  of  soda  (crystals),  ....  3 ounces. 

Distilled  water, 80  ounces. 

Eikonogen, 1 ounce. 

seed’s  eikonogen  developer. 

A.  Sulphite  of  soda  (crystals),  ...  6 ounces. 

(If  granular  sulphite  of  soda  is  used  take  only  3 ounces.) 

Water  (ice  or  distilled),  ....  45  ounces. 
First  dissolve  the  above  and  then  add 

Eikonogen, 1 ounce. 

B.  Carbonate  of  potash, 1^  ounces. 

Water  (ice  or  distilled), 15  ounces. 


Developer.^ — 3 ounces  of  A and  1 ounce  of  B. 

If  more  contrast  is  required,  use  more  of  A ; if  less,  more 
of  B. 

The  developer  can  be  used  repeatedly  by  adding  each 
time  a little  of  each  of  fresh  solutions  A and  B. 

Notice  the  temperature  of  the  room,  as  a slight  variation 
in  this  respect  causes  a difference  in  the  time  it  takes  to  de- 
velop. Temperature  should  be  from  70  to  75  degrees, 
Fahr. 

The  developer  may  be  used  repeatedly,  but  will  work 
slower  when  old  (where  no  addition  of  fresh  has  been 
made).  Fresh  developer  is  better  for  short  exposure,  and 
the  old,  if  the  plate  has  been  fully  timed. 


Development  of  Dry  Plates.  83 

The  quantity  of  eikonogen  (A)  must  be  according  to  the 
density  of  the  negative  wanted. 

If  the  negative  is  too  strong,  use  less.  If  not  strong 
enough,  more. 

Wuestner’s  Eikonogen  Developers. 

FOR  PORTRAITS  AND  LANDSCAPES. 

No.  I. — Dissolve  in  32  ounces  distilled  or  ice  water, 

Sulphite  of  soda,  C.  P.  (crystals),  . 1 ounce. 

Eikonogen, ^ ounce. 

No.  2. — Dissolve  in  32  ounces  distilled  or  ice  water, 

Carbonate  of  potash, 3 ounces. 

Developer. —Take  equal  parts  of  No.  1 and  No.  2. 

This  developer  may  be  used  repeatedly,  and  will  keep  for 
months  if  preserved  in  tightly  closed  bottles.  It  is  of  great 
importance  to  use  only  chemically  pure  sulphite  of  soda  (crys- 
tals). In  order  to  dissolve  the  eikonogen  quickly  it  is  ad- 
visable to  pulverize  the  same  in  a porcelain  mortar. 

FOR  INSTANTANEOUS  EXPOSURES. 

Dissolve  in  300  c.  c.  m.  (or  10  ounces)  distilled  or  ice  water, 

Sulphite  of  soda  crystals,  C.  P. , . 20  grammes  (or  § ounce). 

Carbonate  of  potash, 10  grammes  (or  3-  ounce.  ) 

And  then  add  Eikonogen,  . . . ,10  grammes  (or  ^ ounce). 

Cramer’s  Eikonogen  Developers. 

no.  1. 

Distilled  water, 40  ounces. 

Sulphite  of  sodium  crystals,  ....  2 ounces. 

Eikonogen,  finely  powdered,  1 ounce. 

Keep  the  solution  in  a well  stoppered  bottle. 

no.  2. 


Water, 10  ounces. 

Carbonate  of  potassium, 1 ounce. 


84 


Development  of  Dry  Plates. 
no.  3. 

Water, 10  ounces. 

Bromide  of  potassium,  .....  1 ounce. 

FOR  USE. 

Solution  No.  1, 3 ounces. 

Solution  No.  2, 1 ounce. 

Solution  No.  3, 6 to  12  minims  (or  drops). 

When  the  developer  is  quite  new,  it  will  be  found  neces- 
sary to  add  a little  bromide  solution  (No.  3)  in  order  to 
make  it  perfectly  clear.  The  addition  of  old  developer  will 
answer  the  same  purpose.  The  developer  can  be  used  re- 
peatedly by  occasionally  adding  more  of  solutions  Nos.  1 
and  2,  omitting  the  bromide.  It  produces  plenty  of  inten- 
sity by  simply  leaving  the  plate  in  it  long  enough.  Any  de- 
gree of  softness  can  be  obtained  by  diluting  with  more  or 
less  water,  which  is  also  recommended  during  hot  weather 
and  for  under-exposures. 

Over-exposed  plates  restrain  by  adding  more  solution 
No.  3. 

A.  p.  smith’s  eikonogen  developer. 


A.  Eikonogen  (crystals), 120  grains. 

Water, 16  ounces. 

Glycerine,  2 drams. 

Sulphite  of  soda  (crystals),  ....  2 drams. 

Alcohol, 2 drams. 

Sulphite  of  soda  (crystals),  ....  3)  ounces. 

B.  Water, 16  ounces. 

Carbonate  of  soda  (crystals),  ...  6 drams. 

Carbonate  of  potash, 3 drams. 

Yellow  prussiate  of  potash,  ....  1 dram. 


Developer  : A,  2)4  ounces  ; B,  1 ounce.  Restrain  with 
bromide  of  potassium. 


Development  of  Dry  Plates. 


85 


vansant’s  carbonate  of  lithium  developer. 


Distilled  water, 1 ounce. 

Tartrate  of  sodium  and  potassium,  . .25  grains. 

Sulphite  of  sodium  (crystals),  ....  25  grains. 

Carbonate  of  lithium, 1 grain. 

Pyrogallol, 2 grains. 


Dissolve  in  the  order  given.  When  the  solution  loses  its 
energy  after  frequent  use,  it  may  be  renewed  by  the  addi- 
tion of  a few  grains  of  pyro  or  lithium,  as  may  be  required. 

CLEARING  SOLUTIONS. 


NO.  I. 

Alum, 1 ounce. 

Citric  acid, 1 ounce. 

Sulphite  of  iron, 3 ounces. 

Water,  . 20  ounces. 

NO.  2. 

Alum, .1  ounce. 

Citric  acid, 3-  ounce. 

Water, 15  ounces. 

NO.  3. 

Saturated  solution  of  white  alum,  . . 32  ounces. 

Sulphuric  acid, % ounce. 


INTENSIFIERS. 

No.  1. — Immerse  the  plate  in  a saturated  solution  of 
chloride  of  mercury  ; wash  well  and  flow  with  a dilute  solu- 
tion of  ammonia. 

No.  2.— Whiten  the  film  in  a saturated  solution  of  chlo- 
ride of  mercury  ; wash  and  blacken  in  a 1 to  5 solution  of 
sulphite  of  sodium. 

No.  3. — Saturated  solution  of  bichloride  of  mercury,  10 
ounces  ; iodide  of  potassium,  10  drams.  Dissolve  the  iodide 


86 


Development  of  Dry  Plates. 


in  ten  ounces  of  water,  and  pour  gradually  into  the  mercury 
solution  until  the  precipitate  is  nearly  redissolved.  Add  i 
ounce  of  hyposulphite  of  soda. 

no.  4. 

Bichloride  of  mercury, 10  grains. 

Chloride  of  ammonium, 10  grains. 

Water, ' ; . . . 1 ounce. 

Immerse  the  well  washed  negative  in  this  solution  until 
the  film  is  whitened  ; then  blacken  in  the  following,  after 


thorough  washing  : 

Cyanide  of  potassium, 2 ounces. 

Distilled  water, 48  ounces. 

Nitrate  of  silver, 1 ounce. 

Distilled  water,  . . 6 ounces. 


The  silver  solution  is  poured  gradually  into  the  cyanide, 
stirring  with  a glass  rod.  Allow  the  mixed  solution  to  stand 
a few  days  before  using. 

REDUCING  SOLUTIONS. 

NO.  I. 

Saturated  solution  of  ferri-cyanide  of  potassium,  . 1 ounce. 


Hyposulphite  of  soda  solution,  1 to  5,  . . . .10  ounces. 
NO.  2. 

Potassium  ferri-oxalate, 5 grains. 

Hyposulphite  of  soda  solution,  1 to  5,  . . . . 1 ounce. 

NO.  3. 

Saturated  solution  of  white  alum, 32  ounces. 

Sulphuric  acid, . I ounce. 

NO.  4. 

Perchloride  of  iron,  . 30  grains. 

Citric  acid, 60  grains. 

Water, 16  ounces. 


Note.- — The  negatives  should  be  thoroughly  washed,  in 
all  cases. 


TABLE  SHOWING  COMPARATIVE  VALUE  OF  ALKALINE  CARBONATES  IN  DEVELOPERS. 


Development  of  Dry  Plates . 


87 


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IMPURITIES  IN  PHOTOGRAPHIC  CHEMICALS  AND  TESTS 
FOR  THEM. 


G.  M.  Jones,  in  the  Photographic  Times  Annual. 

SUBSTANCE.  IMPURITIES  POSSIBLY  PRESENT.  TESTS. 

Ammonia Carbonic  Acid Renders  lime-water  milky. 


Dissolved  solid  matter 

Residue  left  on  evaporation. 

Chlorides 

.After  acidulating  with  nitric  acid,  it  gives 
a precipitate  with  silver  nitrate,  which, 
after  washing,  is  readily  soluble  in 
ammonia,  and  re  precipitated  by  nitric 
acid. 

Sulphates 

.After  acidulating  with  nitric  acid,  it 
gives  a precipitate  with  barium  ni- 
trate. 

Lime 

.A  white  precipitate  with  oxalate  of  am- 
monium. 

Lead  is  often  present,  de- 
rived from  the  action  upon 
flint  glass  bottles. 

Nitric  Acid Traces  of  sulphuric  acid 

Black  precipitate,  with  sulphuretted 
hydrogen. 

.After  dilution  it  gives  a precipitate  with 
barium  nitrate. 

Chlorides 

.After  dilution  it  gives  a precipitate  with 
silver  nitrate. 

Peroxide  of  nitrogen 

.The  acid  is  yellow. 

Iodine  may  be  present  if  the  After  dilution  and  cooling  it  gives  a blue 
acid  be  prepared  from  color  with  starch  paste  or  mucilage. 


sodium  nitrate. 

Hydrochloric  Acid Free  chlorine 

.Liberates  iodine  from  solution  of  potas- 
sium  iodide.  See  also  chlorides,  nitric 
acid. 

Sulphuric  acid 

Perchljride  of  iron 

.As  above  for  nitric  acid. 

.Yellow  color.  Brown  precipitate  with 
ammonia  added  till  it  smells  slightly. 

Hydrochloric  Acid Arsenic 

Some  yellow  samples  contain 
no  iron,  but  an  organic 
salt,  and  give  an  alkaline 
ash  on  ignition  of  the  re- 
sidue after  evaporation. 

88 

.Marsh’s  test. 

Reinsh’s  test ; a small  piece  of  copper 
foil  becomes  coated  on  boiling  in  dilute 
acid. 

Development  of  Dry  Plates . 


89 


SUBSTANCE.  IMPURITIES  POSSIBLY  PRESENT.  TESTS. 

Sulphuric  Acid  Bisulphate  of  potassium. . Residue  on  evaporation. 

Sulphate  of  lead . .Milkiness  on  dilution. 

May  be  completely  freed  from  lead  by 
diluting  with  three  or  four  times  as 
much  water,  and  allowing  to  settle. 

No  easy  test  can  be  given,  as  the  sub- 
stances are  so  numerous  ; some  of 
them  volatile,  and  most  require 
separation  from  the  acid  before  de- 
tection. 


When  sold  as  pure,  it  inva- 
riably contains  a trace  of 
iron.  Common  acid  is  also 
liable  to  contain  arsenic, 
selenium,  thallium,  and 
many  other  substances. 

Organic  matter,  as  a piece  of 
straw  in  a carboy  of  acid. 

Acetic  Acid. . Water 


Gives  a brown  color  to  the  acid. 

Does  not  solidify  when  cooled  to  170  C, 
(53°  F). 

White  precipitate  with  silver  nitrate. 


Blackens  in  the  light  after  adding  silver 
nitrate. 


Sulphurous  and  hydrochloric 
acids. 

Aldehyde,  or  volatile  tarry 
matter. 

Organic  sulphuric  acid Smell  of  garlic. 

Citric  Acid. .. . Tartaric  acid Strong  solution  of  potassium  acetate 

added  to  a strong  solution  of  the 
acid  will  deposit  white  crystalline 
bitartrate. 


Pyrogallic  Acid Metagallic  acid Black  residue  insoluble  in  water. 

Silver  Nitrate Free  nitric  acid Reddens  litmus  paper  (neutral  silver 

nitrate  does  not  affect  litmus). 

Potassium  Carbonate.  .Chlorides  and  sulphates. Same  as  for  ammonia. 

Potassium  Iodide. Potassium  Carbonate A strong  solution  in  alkaline  to  test 

paper. 

Sulphates  and  chlorides Same  as  for  ammonia. 

Potassium  iodate A pretty  strong  solution  becomes  yel- 

low from  liberation  of  iodine  on  ad- 
dition of  dilute  sulphuric  acid,  or 
better,  a strong  solution  of  citric 
acid. 

Potassium  Bromide Similar  to  potassium  iodide.  T .See  potassium  iodide. 

Sodium  Carbonate Chlorides  and  Sulphates.  Same  as  for  ammonia. 

Sodium  Chloride Chloride  of  calcium Oxalate  of  ammonium  (after  addition 

Chloride  of  magnesium  of  a little  acetic  acid)  gives  a milki- 

ness or  precipitate,  indicating  cal- 
cium; filter  this  out,  and  add  am- 
moni,  chloride  of  ammonium,  and 
phosphate  of  sodium  (clear  solutions). 
A precipitate  indicates  magnesium 
Both  the  above  cause  dampness  in  wet 
weather.  ^ * i*?3* 

Sodium  sulphate. . . ?.'J.  j.  ."^s  #,07  smlphatos  ib,  ammonia;)  ->  \ J , 

' J o » 3 " ’ ' 1 J J J ... 


9o 


Development  of  Dry  Plates . 


SUBSTANCE.  IMPURITIES  POSSIBLY  PRESENT.  TESTS. 

Potassium  Cyanide. ..  .Potassium  carbonate  nearly  Effervescence  with  dilute  acids,  giving 

Potassium  Hydrate  always  present.  off  a gas  carbonic  anhydride,  which 

renders  lime  water  turbid. 

Kaolin Chalk Effervescence  with  dilute  acids. 

Water Sulphates  and  chlorides Same  as  for  ammonia. 

Calcium  carbonate,  tempor-  Deposited  by  boiling, 
ary  hardness. 

Ammonia,  almost  always  Test  as  for  calcium  chloride,  see  sodium 
present  in  distilled  and  rain  chloride. 

water.  Brown  coloration,  or  precipitate  with 

Nessler’s  re-agent. 

Gelatine Alum Ash,  sometimes  as  much  as  10  per  cent. 

Fatty  matter Separated  by  precipitation  with  alcohol. 

Dissolved  out  by  ether  or  benzine, 
and  left  as  a residue  on  evaporation 
of  the  solvent. 

Ammonium  Bromide..  .Potassium  bromide,  or  other  Leaves  a residue  when  heated. 

non-volatile  bodies.  Same  as  for  chlorides  in  ammonia. 

Ammonium  chloride. 

Pyrogal  ic  Acid. . Powdered  glass Left  behind  on  solution. 

Potassium  Iodide Potassium  bromide The  crystals  of  bromide  are  usually 

more  transparent  than  those  of  iodide, 
but  no  reliance  can  be  placed  on  this. 

Silver  Nitrate  Potassium  nitrate,  sometimes  Will  not  yield  the  full  quantity  of  chlo- 

present  in  the  fused  sticks,  ride  on  precipitation  with  HCI.  Gives 
not  in  the  crystals.  a purple  color  to  flame. 

Calcium  Chloride Calcium  hydrate The  clear  filtered  solution  made  with 

distilled  water  is  alkaline  to  test 
paper,  and  gives  a precipitate  on 
breathing  into  it  through  a tube. 

Pure  (?)  Chemicals  Broken  glass,  bits  of  straw,  These  impurities  either  float  or  sink  on 

generally.  wood,  paper,  etc.  the  solution,  and  may  easily  be  seen. 


TABLES  FOR  THE  CONVERSION  OF  GRAMS  (OR  CUBIC 
CENTIMETERS)  INTO  OUNCES  ANI)  GRAINS. 


CONVERSION  OF  GRAMS  INTO 


CONVERSION  OF  GRAINS  INTO 


GRAINS. 


Grains,  j Grains. 

15-43 
30.86 
46.29 
61.73 
77.16 
92.59 
108.03 
123.46 
133.% 


GRAMS. 

Grams. 

1  0648 

2  1296 

3  1944 

4  -2592 

5  3240 

6  3888 

7  4536 

8  5184 

9 •••••; 5832 


Development  of  Dry  Plates. 


91 


CONVERSION  OF  GRAMS  INTO 
TROY  OUNCES. 


Grams. 

1  

2  


Troy  Ounces. 

...  .03215 
...  . 06430 
...  .09645 
...  .12860 
...  .16075 
...  .I929O 

...  .22505 
...  .25720 
...  .28935 


CONVERSION  OF  GRAMS  INTO 
AVOIRDUPOIS  OUNCES. 


Grams. 

1  

2  

3  

4  

5  

6  

7  

8  

9 


Avoird’s  Ounces. 

03527 

.07054 

IQ58I 

I4IO8 

17635 

.......  .2Il62 

24689 

28216 

31743 


The  above  tables  render  the  conversion  of  the  weights 
in  question  a matter  of  great  ease,  the  error  introduced  in 
the  last  decimal  place  being  trivial. 


The  use  of  the  tables  will  be  best  illustrated  by  an  ex- 
ample. Supposing  that  it  is  desired  to  find  the  equivalent 
in  grains  of  324.51  grams,  we  proceed  by  breaking  up  this 
number  into  the  following  series  of  constituent  parts,  and 
finding  the  grain-equivalent  of  each  part  from  the  table: 


Portions  of  original  number. 

300.  OO 

20.  OO 

4.00 

•50 

.OI 


Equivalents  in  grains. 

4630. 

308.6 

61.73 

7.716 

•I543 

5008. 2003 


The  required  quantity  is  5008.2  grains.  The  numbers 
taken  from  the  table  will,  in  most  cases,  require  a change 
as  regards  tne  position  of  the  decimal  point;  thus,  to  find 
the  value  of  300  grams,  one  refers  to  the  table,  and  finds 
46.30  given  as  the  equivalent,  and  a mere  shifting  of  the 
decimal  point  two  places  towards  the  right  multiplies  this 
by  100,  or  gives  the  required  number.  In  a similar  man- 
ner, by  shifting  the  decimal  place  of  30.86  one  place  to  the 


92 


Development  of  Dry  Plates. 


right  we  obtain  the  value  in  grains  of  20  grams;  while  the 
number  61.7  is  taken  from  the  table  without  alteration  as 
the  equivalent  of  4 grams.  For  .50  the  table  number  must 
have  its  point  shifted  on  to  the  left,  making  it  7.716  instead 
of  77.16;  and  finally,  the  value  of  .01  is  obtained  by  shifting 
the  point  of  15.43  two  places  to  the  left. 

The  above  operations  are,  in  actual  practice,  performed 
with  considerable  speed,  the  .required  equivalents  being 
written  down  one  after  the  other  on  a scrap  of  paper,  and 
then  added  up. 


TABLE  OF  CONTENTS 


— * : 

CHAPTER  I. 

General  Principles, 5 

CHAPTER  II. 

The  Developing  Room, 9 

CHAPTER  III. 

The  Principles  of  Development  — The  Tentative  Method,  . . . .16 

CHAPTER  IV. 

The  Automatic  Method  — Use  of  a Bromide  — Over-Exposure,  . . 25 

CHAPTER  V. 

The  Components  of  the  Developer  and  their  Adjustment,  ....  30 
CHAPTER  VI. 

The  Ferrous-Oxalate  Developer, 35 

CHAPTER  VII. 

The  Pyrogallol  Developer, 40 

CHAPTER  VIII. 

The  Hydrochinon  Developer, 47 

CHAPTER  IX. 

The  Eikonogen  and  Pyrocatechin  Developers, 51 

CHAPTER  X. 

Development  of  Instantaneous  Exposures  — Films  and  Lantern  Slides,  55 
CHAPTER  XI. 

Fixing  and  Washing, 61 

CHAPTER  XII. 

Intensification  and  Reduction, 67 

CHAPTER  XIII. 

Supplementary  Notes, 72 

Formulas  and  Tables, 79 

93 


